A pond appears to be 2.7 m deep. If the refractive index of water is 4/3, find the actual depth of the pond.

Why does stone lying in the sun get heated up much more than water lying for the same duration of time?

The wave lengths for the light of red and blue colours are nearly 7.8 x 10^-7 m and 4.8 x 10^-7 m respectively.

(i) Which colour has the greater speed in a vacuum?

(ii) Which colour has a greater speed in glass?

A sound wave travelling in water has wavelength 0.4 m. Is this wave audible in air? (The speed of sound in water = 1400 ms^-1).