A circular coil of single turn has a resistance of 20$$\Omega$$. Which one of the following is the correct value for the resistance between the ends of any diameter of the coil?

In a solenoid, the current flowing through the wire is I and number of turns per unit length is n. This gives a magnetic field B inside the solenoid. If number of turns per unit length is increased to 2n, what will be the value of magnetic field in the solenoid?

Which one of the following statements is correct about the magnification of an optical microscope?

Colour vision in human eyes is the function of photoreceptor cells named