Human Eye and Colourful World — Science STD 10 — Question

Give the usual name for the following:
A point inside a lens through which the light passes undeviated.

A ray of light strikes a plane mirror at an angle of 40° to the mirror surface. What will be the angle of reflection?

A nuclear reactor has half the length of all its control rods inserted in graphite. What must be done so that the reactor produces more heat? Explain your answer.

Stars twinkle due to refraction in fluctuating atmosphere.

The following questions are about the nuclear reactor of a power plant.
What is the purpose of using the graphite moderator?

How should the two resistances of 2 ohms each be connencted so as to produce an equivalent resistance of 1 ohm?

Name the device which converts electrical energy into mechanical energy.

A current-carrying conductor is placed perpendicularly in a magnetic field. Name the rule which can be.

Which has higher refractive index : water or glass?

Why do electricians wear rubber hand gloves while working with electricity?