Physics
The distance (V) of a virtual image formed by a lens of focal length 15 cm never exceeds a certain finite value, then this value will be:
- less than 15 cm
- between 15 cm to 30 cm
- less than or equal equal to 30 cm
- less than or equal to 15 cm
Answer
less than or equal to 15 cm
Reason — A virtual image whose distance never exceeds a fixed finite value is formed by a concave lens. In a concave lens, the image is always virtual and is formed between the optical centre and the principal focus. Hence, the image distance can never be greater than the focal length of the lens.
Therefore, for a lens of focal length 15 cm, the image distance is less than or equal to 15 cm.
Related Questions
When a blackened bulb thermometer is moved beyond the red region of the visible spectrum, there is a rapid rise in the temperature. This is due to the presence of :
- Infrared radiations
- Ultraviolet radiations
- X-rays
- Radio waves
A fast-moving cyclist stops pedalling on reaching a hilly track. If he continues to move with the acquired energy, then assuming no loss of energy:
- his kinetic energy remains constant at all times.
- his potential energy remains constant at all times.
- his total mechanical energy continuously increases.
- his total mechanical energy remains constant.
Assertion (A) : Tiny air molecules scatter blue light more than red light.
Reason (R) : The refractive index of a medium is greater for blue light than red light.
- (A) is true but (R) is false.
- (A) is false but (R) is true.
- Both (A) and (R) are true and (R) is correct explanation of (A).
- Both (A) and (R) are true and (R) is not the correct explanation of (A).
In the circuit given below, identify the lamp (L1, L2, L3 and L4) whose failure would not interrupt the power supply to the other lamps.
- L1
- L2
- L3
- L4