A telescope uses convex and parabolic mirrors to focus light waves. Ray optics treats light as traveling in straight lines, while wave optics considers it a wave. When light travels from a rarer to denser medium, it bends due to the change in speed. A parabolic mirror collects light and focuses it to a point or small area by curving the path of light rays.

4. telescope

5. convex & parabolic mirrors

7. optics = light
wave optics = thinking of light as a wave
ray optics = light is a ray (St. line)
rarer to denser medium
= light bends
particle theory explains -
it doesnt explain -

8. quantum

9. path
2 D
1
2

10. 3 D
no water
instead of circle
previously, there was a water SURFACE. here there is no surface

11. shape

12. part of sphere

14. he only explained waves forming at the front & not back.
if we draw tangent to secondary wavelets behind, sphere is formed = back wave.

15. is always perpendicular to travelling wave
tubelight
like gaussian surface -

16. if light in x direction
wavefront is in plane y-z