Ray Optics and Optical Instruments — Physics STD 12 Science — Question

A tall man of height 6 feet, want to see his full image. Then required minimum length of the mirror will be-

The net resistance of an ammeter should be small to ensure that:

1. It does not get overheated.
2. It does not draw excessive current.
3. It can measure large currents.
4. It does not appreciably change the current to be measured.

In summer, a mild wind is often found on the shore of a calm river. This is caused due to,

1. Difference in thermal conductivity of water and soil.
2. Convection currents.
3. Conduction between air and the soil.
4. Radiation from the soil.

Between the plates of a parallel plate condenser there is 1mm thick paper of dielectric constant 4. It is charged at 100 volt. The electric field in volt/metre between the plates of the capacitor is(a) 100(b) 100000(c) 25000(d) 4000000

Among which of the following the magnetic susceptibility does not depend on the temperature?

Doping of intrinsic semiconductor is done(a) To neutralize charge carriers (b) To increase the concentration of majority charge carriers (c) To make it neutral before disposal(d) To carry out further purification

A simple microscope has:

If convex lens of focal length 80cm and a concave lens of focal length 50 cm are combined together, what will be their resulting power (a) + 6.5 D (b) – 6.5 D(c) + 7.5 D(d) – 0.75 D