A submarine is observed to rise from a real depth of 80 m to 60 m in water. Calculate the change in apparent depth.
[Refraction index of water \(\frac{4}{3}\)]
Non-luminous object can be seen because they
The wavelength of the first overtone of a note in a closed pipe of length 33 cm is?
A person can focus objects when they lie beyond 75 cm from his eyes. The focal length of the lens required to reduce his least distance of distinct vision to 25 cm is?
