| paraxial ray | rays which form very small angle with principle axis and close to it are called paraxial rays. |
| explain the rules of sign convention | acc. to above convention radius of curvature and focus of concave mirror are -ve and for convex mirror is +ve |
| what does not change during refraction | frequency |
| when is a ray passing through a parallel slab parallel | if the medium is same on both sides of the slab |
| what are the condition for TIR | -ray is going from denser to rarer medium
-angle of incidence should be greater than critical angle |
| spaarkling of diamond | due to TIR inside it. as refractive index for diamond is 2.42 so C=24.41 degree. now the cutting of diamond are such that i>C. |
| optical fibre | in it light through multiple TIR is propagated along the axis of a glass fibre of few microns in which index of refraction of core is greater than that of surrounding |
| mirage | is caused due to TIR where due to heat the refractive index of air near the earth's surface becomes less than above it |
| looming | in polar regions looming takes place due to TIR. here refractive index decreases with height |
| dispersion of light | when white light is incident on a prism then it splits into seven colours |
| angle of dispersion | angle between the rays of extreme colours in the refracted light. |
| achromatic combination | used for deviation without dispersion |
| direct vision combination | used for producing dispersion without deviation |
| displacement method | used for determination of focal length of convex lens in laboratory. |
| why do we prefer to use a convex mirror for observing traffic at our back | because a convex mirror has a more larger field of veiw than a plane mirror or concave mirror |
| a ray incident along normal to a mirror retraces it's path | because in refletion the angle of incidence and reflection is always equal |
| why do images formed by mirrors do not show chromatic aberration | because focal length of mirror is independent of wavelength of light and reractive index of medium |
| light from an object falls on a concave mirror forming a real image of the object. if both the object and mirror are immersed in water, there is no change in the position of image. why? | because the formation of the by reflection does not depend on surrounding medium, there is no change in position of image provided it is also formed in water. |
| why are images formed by TIR much brighter than those formed by mirror | beacuse there is no loss of intensity of light in TIR |
| why does a fish in the pond see a person outside taller than he actually is | because light bends away from the normal as it enters water from air |
| why does just before setting the sun appears to be elliptical | because of refractionof light ray through the atmosphere may cause difernt magnification in mutually perpendicular directions |
| when does a covex lens behaves as a concave lens | when placed in a medium of refractive index greater than the refractive index of its material because light in that case will travel through the convex lens from denser to rarer medium. it will bend away from the normal |
| if lower half of a lens is covered with a black paper, then what happens to the image | full image is formed with less intensity |
| axial or longitudinal chromatic aberration | if the object is at infinity, then longitudinal chromatic aberration is equal to the difference in focal length for the red and the violet rays |
| achromatism | if two or more lenses are combined together in such a way that this combination produces images due to all colours at the same point then this combination is known as achromatic combination of lenses |
