Ray Optics and ...

Assertion: Two convex lenses joined together cannot produce an achromatic combination.
Reason : The condition for achromatism is $$\dfrac{\omega _1}{f_1}+\dfrac{\omega _2}{f_2}=0$$ where symbols have their usual meaning.

When light moving in one medium falls at the surface of another medium, _______ light returns back to the same medium.

In an electron microscope the accelerating voltage is increased from 20 kV to 80 kV, the resolving power ofthe microscope will become.

Assertion: A double convex lens ($$\mu$$ = 1.5) has focal length 10 em, When the lens is immersed in water ($$\mu$$ = 4/3) its focal length becomes 40 cm.
Reason: $$\frac{1}{f}=\frac{\mu_1-\mu_m}{\mu_m}=\left ( \frac{1}{R_1}-\frac{1}{R_2} \right )$$.

Sodium lamps are used in foggy conditions because:

Refraction occurs due to:

Which phenomena of light makes a pool of water appears to be less deep than it actually is?

Why do high rise buildings have a red light on the top of the building?

The sun appears red at the time of sun-rise and sun-set. This is because:

Refractive index of diamond with respect to glass is $$1.6$$ and absolute refractive index of glass is $$1.5$$. Find out the absolute refractive index of diamond.