The size of the hole of a pin hole camera is increased. The resultant image formed becomes

The refractive index of a medium relative to air is 1.8. Calculate to the nearest degree, the critical angle for the medium

A converging lens of focal length 15cm forms a virtual image at a point 10cm from the lens. Calculate the distance of the object from the lens

In a compound microscope, the image formed by the objective lens is at a distance of 3.0cm from the eye lens. Calculate the focal length of the eye lens

A pulse of a sound is transmitted from a ship and the reflection from the sea bed is recorded after 0.2s. Calculate the depth of the sea. [Take speed of sound in sea water = 1560ms^-1]