From the figure given below, the refractive index of medium B with respect to medium A (_Aμ_B) is:

1. $\dfrac{\text {sin }45\degree}{\text {sin }30\degree} \\[1em]$
2. $\dfrac{\text {sin }30\degree}{\text {sin }45\degree} \\[1em]$
3. $\dfrac{\text {sin }45\degree}{\text {sin }60\degree} \\[1em]$
4. $\dfrac{\text {sin }60\degree}{\text {sin }45\degree} \\[1em]$

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 :

1. Infrared radiations
2. Ultraviolet radiations
3. X-rays
4. Radio waves

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:

1. less than 15 cm
2. between 15 cm to 30 cm
3. less than or equal equal to 30 cm
4. less than or equal to 15 cm

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.

1. (A) is true but (R) is false.
2. (A) is false but (R) is true.
3. Both (A) and (R) are true and (R) is correct explanation of (A).
4. Both (A) and (R) are true and (R) is not the correct explanation of (A).