IMPORTANT POINT ON LIGHT

1)Light travels in straight line in a homogeneous medium this is called Rectilinear Propagation of Light

2)Example of rectilinear propagation of light is formation of shadow, formation eclipses, formation of image in pin hole camera

3)The darkest region of a shadow is called umbra


4)The partially dark region of a shadow is called penumbra

5)Real image can be cast on the screen and Virtual can not be cast on screen

6)Pin hole camera image is real and inverted

7)Image formed in plane mirror is virtual and erect

8)Concave mirror is made by silvering the outer surface

9)Convex mirror is made by silvering the inner surface

10)Concave mirror is used as a Doctor's headmirror

11)Convex mirror is used as a rear view finder of motor vehicles

12)Convex mirror is used as a reflector in street lamp

13)Concave mirror is used as a reflector of torch light, Search light

14)The twinkling of stars is caused due to refraction

15)Early Sun and Late Sunset is caused due to refraction

16)Apparent bending of a stick under water is caused due to refraction

17)For Total Internal Reflection a light must travel from denser to rarer medium

18)Example of Total Internal Reflection periscope, Mirage in desert

19)Rainbow is caused due to the dispersion as well as total internal reflection

20)In a vacuum, all these colours travel with the same speed but in a transparent medium they have different speeds.