If the mirror moves with speed v. then image will appear to approach u with speed 2v.. Because wrt the mirror the image moves with speed v and wrt ground it will move with v(wrt mirror) + v(of mirror) = 2v

An air bubble in water that is shaped like a normal glass lens would have roughly the opposite effect of the glass lens. There are at least three ways to see why.

If we consider a convex bubble and a concave glass lens in air or vacuum, we can see that the interface between water and air in the bubble and the glass and air in the lens is really exactly the same: the material with the higher index (water or glass) curves in and the material with the lower index of refraction curves out. The only difference is that with the bubble, two of these interfaces are face to face and in the lens, they are back to back. Thus the convex bubble and the concave lens should behave the same.

The second way is to do some ray tracing. A ray of light is bent toward the perpendicular when entering a higher index medium (like water or glass) and away from the perpendicular when exiting a higher index medium. For a concave bubble, a ray going through the center of the bubble will not be refracted at all at either transition. A ray perpendicular to the plane of the "lens" formed by the bubble will be refracted away from the center of the bubble as it enters the bubble and then only partially back toward the original direction as it exits the bubble. THe net effect is one of divergence.

The third method is to analyze a spherical lens using the lens-maker's formula. This will give a negative focal length for a convex lens of air inside water.

Light from the Sun appears white but it actually consists of many different colours. We can see these different colours of light in a rainbow or when white light passes through prism. As the white light from the Sun travels through the Earth’s atmosphere, it collides with particles of air.  The different colours, or wavelengths, of light are scattered by these collisions by different amounts.  Blue light (shorter wavelengh) is scattered more than others.

So, when the Sun is high in the sky, blue light is scattered in all directions as sunlight passes through the atmosphere and we see the sky as blue.

The three types of spectra are called “a continuous spectrum” (or continuum emission), “an emission line spectrum” and “an absorption line spectrum”

A continuous spectrum When Newton did his famous experiment with a prism and sunlight, he noted that the Sun produced a “rainbow” of colours. This is a continuous spectrum. (However, as I will discuss in a future blog, if he had been able to produce a more detailed spectrum he would have noticed some subtleties on this continuous spectrum). So, light from the Sun, and any star, produces a continuous spectrum.

We also get a continuum spectrum from a hot solid, so for example the light produced by incandescent light bulbs is a continuum spectrum. These kinds of bulbs give off light by a very thin coil of metal, the filament, (usually tungsten) getting extremely hot from having an electric current passed through it. When the filament gets to thousands of degrees, it gives off light.

An emission line spectrum If, instead of looking at the spectrum of the Sun we were to look at the spectrum of an object like Messier 42 (the Orion nebula), we would notice a very different kind of spectrum. Rather than being a continuous spectrum, we would see a series of bright lines with a dark background. We would also see an emission line spectrum if we were to look at the spectrum from one of the fluorescent light sources which are now replacing the incandescent lights in houses.

An absorption line spectrum An absorption line spectrum is in some ways the converse of an emission line spectrum. Rather than seeing a series of bright lines on a dark background, one sees dark lines on a continuous spectrum.

A spectrometer or spectrograph is an instrument attached to a telescope to analyze the radiation from astronomical objects. It uses a prism or a grating to spread the light from the object into a spectrum, a rainbow of colours. This allows astronomers to detect many of the chemical elements by their characteristic fingerprints. Typically these are dark bands in specific locations in the spectrum caused by energy being absorbed as light passes through an atmosphere of gas. If the object is glowing by its own light, it will often show bright lines caused by the glowing gas itself. These lines are named for the elements which cause them, such as the Hydrogen Alpha, Beta, and Gamma lines. The spectrometer is the most powerful and widely used tool in astronomy aside from the telescope itself. Almost all of our knowledge of the chemical makeup of the universe comes from spectra.

Although the dispersion of white light is useful when we want to look at the spectrum of the light it is a real problem in optical instruments such as telescopes. The lenses in these instruments disperse different colours by different amounts and so bring the different colours to different foci. The images formed are coloured and blurred. It is therefore necessary to deviate the light without dispersing it, and prisms and lenses that do this are called achromatic (Greek, 'without colour').

 Dispersive power of prism    The refractive index of the material of the prism can be calculated by the equation.               -------------------(3)  Where, D is the angle of minimum deviation, here D is different for different colour .    Consider two colour green and violet, corresponding minimum deviation is DG and DV ,corresponding  refractive index is.     ,                  -------------------(4) There for dispersive power is.          -------------------(5) Where          -------------------(6)

Lactometer is a device used for finding the purity of a milk sample. It works on the principle of Archimede's principle that a solid suspended in a fluid will be buoyed up by a force equal to the weight of the fluid displaced. If the milk sample is pure, then the lactometer floats on it and if it is adulterated or impure, then the lactometer sinks.

The formula for maximum number of electrons in a shell is given by 2N^2, where N stands for the number of shells. the electron shells is named as K, L, M, N, and so on in the ascending order. so M is the 3rd shell so no. of electrons in m shell= 2(3)^2= 18.

Inspite of the maximum number of electrons in the M shell is 18, but when M shell is the last shell it contains maximum upto 8 electrons, to attain the stable condition of an electron.

An atom comprises of two charges, positive and negative. the neutral particles an the positive particles have mass and is located at the centre of the atom. the negative charges that is the electrons is negligible in mass and also rotates around the nucleus (portion containing nutrons and protons) of the atom. the neculeus obviously attracts the electrons as the opposite charges attract each other. inspite of this attraction the electons do not collide on the neucleus, because these electrons revolve round the specific shell or energy bands. there are different shells specified for different electrons namely K,L,M,N, etc. if a electron looses or gain energy it jumps up or down from one shell to another.

1/F = 1/f1 + 1/f2

Combined focal length (F): =f1f2/[f1 + f2]

If the image and object are in the same medium it is just the image distance divided by the object distance. negative sign is used on the linear magnification equation as a reminder that all real images are inverted.

a permanent magnet can be de magnetised in the following ways.

i. droppin it from height several times.

ii. hammering it

iii. passing electric current

iv. forcebly  keeping it near to the like poles of other strong magnets.

if we pass electricity through a wire it forms a magnetic field arround it. when a insulated copper wire is wound round a soft iron core and electricity is is allowed to flow through it the soft iron core gets magnetised. the soft iron core acts as a temporary magnet. the soft iron gets demagnetised as soon as the current stops flowing though the copper wire. this system of converting the soft iron core into a temporary but strong magnet while passing electricity is known as electromagnetism.

First law:    When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a force. Second law:    The vector sum of the forces F on an object is equal to the mass m of that object multiplied by the acceleration vector a of the object: F = ma. Third law:    When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.

No surface is perfectly smooth. the microscopic view of the surfaces shows the roughness in the form of small hills. friction is there between two surfaces. the hills of the two surfaces actually collieds with each other and thus causing an interlocking between the two surfaces. the friction is due to this interlocking. when force in the opposite direction is applied these hill gets interlocked among themselves and resists the movement, this is the cause of friction.

yes, if the eath atttracts apple the apple also attracts the earth. but the apple move towards the earth because the mass of apple is very less as comapared to that of the earth. 

KE=1/2 m.v^2

when the velocity is trippled the the kinetic energy is multiplied 9 times.

when the electric bulb is lighted the electrical energy is transformend into light and heat energy.

bats can produce ultra sonic sound whic is inaudiable to humans. these ultrasonic waves gets reflected back on getting hitted to somthing. these may be prey or an obstacle for the bat. on receiving the reflection of the ultrasonic waves sent by it the bat judges the shape size and nature of the obstacle in front of it. 

distance of the obstacle = total distance travelled / 2

distance = timeXvelocity

               = 4s X 340m/s

               =1360m

therefore the actual distance of the obstacle = 1360/2=680m

Potential Energy- The energy possesed by a body by virtue of its position is known as potential energy. Example- streched rubberband.

A free-falling object has an acceleration of 9.8 m/s/s, downward (on Earth). This numerical value for the acceleration of a free-falling object is such an important value that it is given a special name. It is known as the acceleration of gravity - the acceleration for any object moving under the sole influence of gravity. A matter of fact, this quantity known as the acceleration of gravity is such an important quantity that physicists have a special symbol to denote it - the symbol g. The numerical value for the acceleration of gravity is most accurately known as 9.8 m/s/s.

 Beating of a carpet with a stick; makes the carpet come in motion suddenly, while dust particles trapped within the pores of carpet have tendency to remain in rest, and in order to maintain the position of rest they come out of carpet. This happens because of the application of Newton’s First Law of Motion which states that any object remains in its state unless any external force is applied over it. This law is also known as law of inertia due to rest.

Newton's laws of motion are three physical laws that, together, laid the foundation for classical mechanics. They describe the relationship between a body and the forces acting upon it, and its motion in response to those forces. They have been expressed in several different ways, over nearly three centuries, and can be summarised as follows.

First law:When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by a force.

Second law:The vector sum of the forces F on an object is equal to the mass m of that object multiplied by the acceleration vector a of the object: F = ma

Third law:When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.

Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity usually means relative density with respect to water. The term "relative density" is often preferred in modern scientific usage. It is defined as a ratio of density of particular substance with that of water

(i) A body is said in uniform acceleration when its motion is along a straight line and its velocity changes by equal magnitude in equal interval of time.

(ii)A body is said in non-uniform acceleration when its motion is along a straight line and its velocity changes by unequal magnitude in equal interval of time.

unit of power is watt = J/sec

Sound(mechanical waves) waves in air (and any fluid medium) are longitudinal waves because particles of the medium through which the sound is transported vibrate parallel to the direction that the sound wave moves.The back and forth vibration of the sound source(membrane, etc) causes individual air molecules (or a layer of air molecules) in the region immediately to the right of the string to continually vibrate back and forth horizontally. The molecules move rightward as the membrane moves rightward and then leftward as the string moves leftward. These back and forth vibrations are imparted to adjacent neighbors by particle-to-particle interaction. Other surrounding particles begin to move rightward and leftward, thus sending a wave to the right. Since air molecules (the particles of the medium) are moving in a direction that is parallel to the direction that the wave moves, the sound wave is referred to as a longitudinal wave. The result of such longitudinal vibrations is the creation of compressions and rarefactions within the air

Uses of ultrasound are as follows:

1. in medical fiels, to detect any abnormality in organs of the body.

2. in sonar, to measure the depth of the sea.

3. in mechanical construction, in form of NDT (n destructive testing) to detect the faults of the construction.

4. in training purpose of animals such as dogs.

A sound wave is the pattern of disturbance caused by the movement of energy traveling through a medium (such as air, water, or any other liquid or solid matter) as it propagates away from the source of the sound. The source is some object that causes a vibration, such as a ringing telephone, or a person's vocal chords. The vibration disturbs the particles in the surrounding medium; those particles disturb those next to them, and so on. The pattern of the disturbance creates outward movement in a wave pattern, like waves of seawater on the ocean. The wave carries the sound energy through the medium, usually in all directions and less intensely as it moves farther from the source.

Ultrasounds are sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is no different from 'normal' (audible) sound in its physical properties, except in that humans cannot hear it.Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz.

The human ear can respond to minute pressure variations in the air if they are in the audible frequency range, roughly 20 Hz - 20 kHz.

Nuclear plants, like plants that burn coal, oil and natural gas, produce electricity by boiling water into steam. This steam then turns turbines to produce electricity. The difference is that nuclear plants do not burn anything. Instead, they use uranium fuel, consisting of solid ceramic pellets, to produce electricity through a process called fission.

Nuclear power plants obtain the heat needed to produce steam through a physical process. This process, called fission, entails the splitting of atoms of uranium in a nuclear reactor. The uranium fuel consists of small, hard ceramic pellets that are packaged into long, vertical tubes. Bundles of this fuel are inserted into the reactor.

A mirage is an optical phenomenon that creates the illusion of water and results from the refraction of light through a non-uniform medium. Mirages are most commonly observed on sunny days when driving down a roadway. As you drive down the roadway, there appears to be a puddle of water on the road several yards (maybe one-hundred yards) in front of the car. Of course, when you arrive at the perceived location of the puddle, you recognize that the puddle is not there. Instead, the puddle of water appears to be another one-hundred yards in front of you. You could carefully match the perceived location of the water to a roadside object; but when you arrive at that object, the puddle of water is still not on the roadway. The appearance of the water is simply an illusion.

Ray diagrams can be used to determine the image location, size, orientation and type of image formed of objects when placed at a given location in front of a concave mirror. Ray diagrams provide useful information about object-image relationships, yet fail to provide the information in a quantitative form. While a ray diagram may help one determine the approximate location and size of the image, it will not provide numerical information about image distance and object size. To obtain this type of numerical information, it is necessary to use the Mirror Equation and the Magnification Equation. The mirror equation expresses the quantitative relationship between the object distance (do), the image distance (di), and the focal length (f). The equation is stated as follows:

1/f= 1/do+1/di The magnification equation relates the ratio of the image distance and object distance to the ratio of the image height (hi) and object height (ho). The magnification equation is stated as follows:

m= hi/ho =-di/do

These two equations can be combined to yield information about the image distance and image height if the object distance, object height, and focal length are known.

As a demonstration of the effectiveness of the mirror equation and magnification equation, consider the following example problem and its solution.

Metals

Physical Properties

• Usually solid when in room temperature except mercury, which is liquid
• Have a lustrous or shiny look
• Are good conductors of heat and electricity
• Have a high melting and boiling point
• Have a high density, are heavy for their size
• Are malleable, i.e. can be hammered into sheets
• Are ductile, i.e. can be drawn into wires
• Are opaque as a thin sheet
• Are sonorous, i.e. make a bell-like sound when struck

Chemical Properties

• Have 1-3 electrons in the outer shell of each metal atom
• Corrode easily, i.e. damaged by oxidation such as tarnish or rust
• They lose electrons easily
• They form oxides that are basic in nature
• Have lower electro-negativities
• Are good reducing agents

Non-metals

Nonmetals include carbon, hydrogen, nitrogen, phosphorous, oxygen, sulfur, selenium, halogens and the noble gases.

Physical Properties

• Are not lustrous, have a dull appearance
• Are poor conductors of heat and electricity
• Are non-ductile solids
• Are brittle solids
• May be solids, liquids or gases at room temperature
• Are transparent as a thin sheet
• Are not sonorous, i.e. do not make a bell-like sound when struck

Chemical Properties

• Usually have 4-8 electrons in their outer shell
• They readily gain or share valence electrons
• They form oxides that are acidic in nature
• They have higher electro-negativities
• Are good oxidizing agents

The strength of the magnetic field produced by a current carrying solenoid depends on:

The number of turns - larger the number of turns, greater is the magnetism produced The strength of the current - when current increases, magnetism also increases Nature of 'core-material' used in making the solenoid - if we use soft-iron as a core for the solenoid, then it produces the strongest magnetism

persistence of vision. the retention of a visual image for a short period of time after the removal of the stimulus that produced it: the phenomenon that produces the illusion of movement when viewing motion pictures.

heat is produced from splitting atoms – a process called nuclear fission.