Who among the following has explained the phenomenon of photoelectric effect?

Two metallic wires A and B are made using copper. The radius of wire A is r while its length is l. A DC voltage V is applied across the wire A, causing power dissipation P. The radius of wire B is 2r and its length is 2l and the same DC voltage V is applied across it causing power dissipation P₁. Which one of the following is the correct relationship between P and P₁ ?

Consider the following statements about a solenoid.

1. The magnetic field strength in a solenoid depends upon the number of turns per unit length in the solenoid.

2. The magnetic field strength in a solenoid depends upon the current flowing in the wire of the solenoid.

3. The magnetic field strength in a solenoid depends upon the diameter of the solenoid.

Which of the statements given above are correct?

Light year is a unit of measurement of