Light waves are electromagnetic/transverse.
visible range 3900-7800 angstrom
speed is maximum in vacuum- 3 x 10^8 m/s
time taken from sun- 8 min 20 sec, from moon - 1.28 sec
Plane mirror- to see his full image, a person requires a mirror of his half size.
Use of concave mirror-
- as shaving glass
- reflector of head light
- in solar furnaces
Use of convex mirror-
- rear view mirror
- sodium reflector lamp
Illustration of total internal reflection-
- sparkling of diamonds
- mirage in desert
Human least distance distinct vision- 25 cm
Unit of power of lens is Dioptre, P =1/f
- The refracted ray will bends away from the normal. This is the case when incident ray in a denser medium refracts into a rarer medium and vice versa.
If several thin lenses of focal length f1, f2, f3,... are in contact, the effective focal length of their combination is given by 1/f1 + 1/f2 + 1/f3 +…… In terms of power, can be written as P = P1 + P2 + P3 … where P is the net power of the lens combination.
- Dispersion is the splitting of light into its constituent colour.
- Magnifying power m of a simple microscope is given by m = 1 + (D/f), where D = 25 cm is the least distance of distinct vision and f is the focal length of the convex lens.
TRICK
- Myopia- (word is short, so short-sightedness) and sightedness means clearly visible, so in Myopia, person can see clearly nearby objects, while have issue to see far objects. It can be cured by Concave lens. (short will get cured by long, concave is longer word than convex).
- Hypermetropia - (far-sightedness)- convex lens is used to cure it.