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प्रश्न
State the condition of the following:
A lens has both its focal lengths equal.
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उत्तर
If the medium on both sides of the lens is same, the first and second focal lengths are equal.
संबंधित प्रश्न
The diagram below shows a lens as a combination of a glass slab and two prisms.
- Name the lens formed by the combination.
- What is the line XX’ called?
- Complete the path of the incident ray AB after passing through the lens.
- The final emergent ray either meets XX’ at a point or appears to come from a point on XX’. Label it as F. What is this point called?

The diagram given below shows the position of an object OA in relation to a converging lens whose foci are at F1 and F2.

Describe how the distance of the image from the lens and the size of the image change as the object is moved towards F1.
How will you differentiate between a convex and a concave lens by looking at a distant object.
How will you differentiate between a convex and a concave lens by looking at a printed page?
State the nature and position of the object on the principal axis to obtain a real and magnified image.
When does a ray of light falling on a lens pass through it undeviated?
Complete the following diagram and state what happens to the ray of light after refraction through the lens.

Mixture of red + blue + green is passed through a convex lens as shown in the diagram below. State whether the ray passes through a single point or through different points on the principal axis after refraction.

