 Click to Chat

1800-1023-196

+91-120-4616500

CART 0

• 0

MY CART (5)

Use Coupon: CART20 and get 20% off on all online Study Material

ITEM
DETAILS
MRP
DISCOUNT
FINAL PRICE
Total Price: Rs.

There are no items in this cart.
Continue Shopping
`        For concave and convex lenses, prove r= f/2........`
11 months ago

```													The focal length of a spherical mirror is equal to half of its radius of curvature 			{f = 1/2 R}.							Proof: In below figure1 and 2, a ray of light BP' travelling parallel to the principal axis PC is incident on a spherical mirror PP'. After reflection, it goes along P'R, through the focus F P is the pole and F is the focus of the mirror. The distance PF is equal to the focal length f. C is the centre of curvature. The distance PC is equal to the radius of curvature R of the mirror. P'C is the normal to the mirror at the point of incidence P'. For a concave mirror:In above figure,																											∠BP'C						=						∠P'CF (alternate angles)																and ∠BP'C						=						∠P'F (law of reflection,∠i=∠r)																Hence ∠P'CF						=						∠CP'F																∴ FP'C is isosceles. 																Hence, P'F						=						FC																														If the aperture of the mirror is small, the point P' is very close to the point P, 																														then P'F						=						PF																∴ PF						=						FC																 						=						1/2						PC																or f						=						1/2						R For a convex mirror: In above figure,																														∠BP'N						=						FC∠P' (corresponding angles)																∠>BP'N						=						∠NP'R (law of reflection, ∠i=∠r) 																and ∠NP'R						=						∠CP'F (vertically opposite angles) 																Hence ∠FCP'						=						∠CP'F																∴ FP'C is isosceles. 																Hence, P'F						=						FC																														If the aperture of the mirror is small, the point P' is very close to the point P.																														Then P'F						=						PF																∴PF						=						FC																 						=						1/2						PC																or f						=						1/2						R
```
11 months ago
```							I have told to prove it for lenses !
```
11 months ago
Think You Can Provide A Better Answer ?

## Other Related Questions on Discuss with Askiitians Tutors

View all Questions »  ### Course Features

• 728 Video Lectures
• Revision Notes
• Previous Year Papers
• Mind Map
• Study Planner
• NCERT Solutions
• Discussion Forum
• Test paper with Video Solution  ### Course Features

• 731 Video Lectures
• Revision Notes
• Test paper with Video Solution
• Mind Map
• Study Planner
• NCERT Solutions
• Discussion Forum
• Previous Year Exam Questions