RBSE Class 12 Physics Chapter 9 — Ray Optics and Optical Instruments: Most Repeated Questions (2013–2026)

1/f=1/u+1/v

All solved questions for this chapter are in the full RBSE Physics PYQ book.

Total internal reflection (TIR) is the phenomenon where a ray of light traveling in a denser medium is completely reflected back into the same medium at the interface with a rarer medium

All solved questions for this chapter are in the full RBSE Physics PYQ book.

As, CP=R

FP=f

In △ CFM :

∠i=∠r

CF≅FM-(1)

Also, FM≅FP-(2)

From (1) and (2) :

CF≅FP -(3)

Now, CP=CF+FP

Substituting (3) into the equation above:

R=FP+FP

R=2FP

Substituting the variables:

R=2f

All solved questions for this chapter are in the full RBSE Physics PYQ book.

(n₂-n₁)/R₁=n₂/v^'-n₁/u --- (1)

(n₁-n₂)/R₂=n₁/v-n₂/v^' --- (2)

Adding (1) & (2)

(n₂-n₁)/R₁+(n₁-n₂)/R₂=n₁/v-n₁/u

(n₂-n₁)/R₁-((n₂-n₁))/R₂=n₁(1/v-1/u)

(n₂-n₁)(1/R₁-1/R₂)=n₁(1/f)

((n₂-n₁))/n₁(1/R₁-1/R₂)=1/f

∴1/f=(n₂/n₁-1)(1/R₁-1/R₂)

1/f=(n-1)(1/R₁-1/R₂)

The size, position, and nature of the image remain unchanged because every point on the mirror contributes to forming the full image. However, the image's intensity or brightness will decrease since the total amount of reflected light is reduced

Lateral shift is the perpendicular distance between the incident ray and the emergent ray when light passes obliquely through a rectangular glass slab

OR Define lateral shift. Derive the lens maker's formula 1/f=(n₂₁-1)(1/R₁-1/R₂) . Draw necessary ray diagram. (where symbols carry usual meaning). [1+2+1=4M]

All solved questions for this chapter are in the full RBSE Physics PYQ book.

(1) ​A compound microscope is built around a system of two converging lenses housed in a tube:

1.​The Objective Lens (near the object) creates a real, magnified, inverted image

2. ​The Eyepiece (near the eye) acts as a simple magnifier, viewing and further enlarging this real image to produce the final, highly magnified, virtual image observed by the user

​These lenses are mounted on an arm and base, and the system includes an illuminator and focus knobs for adjustment

m=( height of image )/( height of object )

m=A^''B^''/AB

Multiply and dividing RHS by A^'B^'

m=A^''B^''/AB×A^'B^'/A^'B^'

m=A^''B^''/A^'B^'×A^'B^'/AB

m=m₁×m₂

(2) The power of a lens is a measure of its ability to converge or diverge light rays, and is defined as the reciprocal of its focal length in meters

m=( height of image )/( height of object )

m=A^''B^''/AB

Multiply and dividing RHS by A^'B^'

m=A^''B^''/AB×A^'B^'/A^'B^'

m=A^''B^''/A^'B^'×A^'B^'/AB

m=m₁×m₂

OR

What do you understand by power of lens? Draw a ray diagram for the formation of image by a compound microscope and derive its formula for magnification. [4M] (RBSE 2025)

All solved questions for this chapter are in the full RBSE Physics PYQ book.