FACTS TO REMEMBER
1. Speed of light is maximum in vacuum.
2. Longitudinal waves can’t be polarized.
3. Rainbow are always formed in direction opposite to the sun.
4. The frequency of visible light varies between 400 nm to 700 nm.
5. Colour blindness was first discovered by Homer (1976).
6. Focal distance of tens is maximum for red light and minimum for violet fight
7. 3-D Image is known as hologram.
8. If a transparent material is invisible in any liquid, then both of them have the same refractive index.
9. Magnifying glass is convex lens of small focal lengths’- If two mirrors are at an angle of 75° then the number of images is 5.
10.Human eyes have convex lens.
11.Raman Effect is related to scattering.
12.Optical fibers works on the principle of total internal reflection.
13.Hypo or radium thiosulphate is used for fusing in photography.
14.Power of sunglass is zero.
15.Heat energy are transmitted as infra-red rays.
16.The first use of telescope for research was by Galeleo Galilie of Italy in 1609.
17.Power measures the degree of divergence or convergence and is measured in diopetres.
18.Negative sign denotes divergence or a concave lens. v Positive sign is for convergence or a convex lens.
19.Air bubble in water behaves as concave lens.
20.As temperature of medium increases, its refractive index increase.
21.Refractive index of a material is independent of angle of incidence.
22.Ammonia is used as a coolant in refrigerator.
23.100°C = 212,°F = 373, K=80R
24.Bolometer is used for detection of infra-red rays.
25.Specific heat of water is 1.0 calorie/gm-°C.
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