Why is a photodiode preferable used in the reverse bias condition for measuring light intesity?

What is interference of light? Write two essential conditions for sustained interference pattern to be produced on the screen. Why interference pattern is not detected when two coherent sources are far apart?

Why do we prefer to use a wrench with a long arm?

Why alternating current is used in place of direct current in measuring the electrolytic conductance.

Draw the circuit diagram of a common emitter n-p-n transistor as an amplifier. Would you prefer to use a transistor as a common base or a common emitter amplifer and why?

A LASER is a source- of very intense, monochromatic, and unidirectional beam of light. These properties of a laser light can be exploited to measure long distances. The distance of the Moon from the Earth has been already determined very precisely using a laser as a source 'of light. A laser light beamed at the Moon takes 2.56 s to return after reflection at the Moon’s surface. How much is the radius of the lunar orbit around the Earth?

Why is red light used as a danger signal ?