Refractions HOTS Flashcards
what are the results of the glass slab experiment
-light undergoes two times relationship: first time is from air to glass and 2nd time is from glass to air.
- angle of incidence is equal to angle of emegrnece
-emergent ray is parallel to incident ray
-when angle of incidence increases angle of reflection icreases since sin i b sin r is a constant.
when does the light give no refraction while passing from two media
i) when the light ray falls normally, perpendicularly at 90 degrees, no refraction takes place. snell’s law fails.
ii) when the optical density of both media are the same
give the applications of convex lens
1) At infinity- used in astronomical telescope
2) Beyond 2F- used in camera
3) At 2F1 -used in terrestrial telescope
4) Between F1& 2F1-used in cinema projector/compound microscope
5) At F1 - used in search lights
6) Between F1 & O -used in simple microscope or magnifying glass
dis cuss the image formation when
i)lens is half covered with the blackpaper
when the lens is half covered by black paper, the lens produces a complete image.the position of the image and the nature depends on the posn of the obj and the nature of the lens.
intensity of the img ∝ (aperture)^2
when its covered
intensity ∝ (1/2)^2
the intensity will be 1/4 times the intensity of the img when the lens is not covered.
what is the relation between intensity and distance between lens and light source
as the light source(obj) comes closer to the lens. the intesity of the image decrease.
Number of parallel rays falling in the lens become less when the source is close to the lens. Slanting rays will be falling,,so intensity decreases
what does the focal length of lens depend on
focal length of a lens depends on the nautre of the surrounding medium. the material that the lens is made of and colour of the light fallingon it.
what happens to the f of a lens when monochromatic red light falls on it rather than blue light
since n is inversly proporitonal to lambda, the red light has more lambda, the focal length increases
lambda∝ f
f∝ 1/μ−1
and μ∝ 1/λ
what happens when convex/concave lens is placed in water
concave lens does not show any change in focal length. abut convex lens the focal length changes, because power decreases.
how do distinquish plane glass, convex lens, concave lens
take a printed paper, if the letters are the same size then its plane glass, if the letters are enlarged then the lens in convex lens and if the letters re diminished then the lens is concave lens.
a fisher man always aims for the tail of the fish why
due the refraction of light from water to air, the light ray moves away from the normal. the fisher sees only the apparent position of the fish. The actual position is lower than the apparent one. so when he aims for the tail of the apparent position his spear hits the head of the actual fish.
what happens when a convex lens of focal length 15cm is cut vertically into two halvs
when we divide the lens into two halves the focal length is dividedinto 2
f1=f2
let f1=f2=f
1/F=1f1+1/f2
1/15-1/f+1/f
1/15=2/f
f=30cm
what is optical density
optical density is the physical property of transparent media, it is the treatment of light by the medium. The optical density is inversely proportional to the speed of light. iN certain media such as air,h2 gas, vacuum, the light travels fast. these are known as OPTICALLY RARER MEDIA. While in some media, such as ruby diamond and flint glass, the light travels slower. these are known as OPTICALLY DENSER MEDIA.
what is optical density and mass density
optical density and mass density are two different entities,optical density is the ability of a medium to refract light while mass density the mass per unit volume of a substance. optical density is directly proportional to refractive index. substances having higher optical density have lower mass density and vice versa. For example, kerosene has lower mass density but bigher optical density than water.
give a pair of media whose optical density is almost the same
glycerin and turpentine oil
provide examples of phenomena caused by refraction
-a stone/coin kept at the botton of a bucket filled with water appears to be raised.
- a lemon/egg in a glass of water appears to be some what bigger in size.
-a pencil, partly immersed in water in a glass, appears to be bent at the water surface
- the letters of a newspaper seems to be raised when seen through a glass slab.
