A convex lens of focal length $40 \mathrm{~cm}$ forms an image of an extended source of light on a photoelectric cell. A current I is produced. The lens is replaced by another convex lens having the same diameter but focal length $20 \mathrm{~cm}$. The photoelectric current now is:

The curve drawn between velocity and frequency of photon in vacuum will be a

The photo-electrons emitted from a surface of sodium metal are such that

In photo electric effect

$A.$ The photocurrent is proportional to the intensity of the incident radiation.

$B.$ Maximum Kinetic energy with which photoelectrons are emitted depends on the intensity of incident light.

$C.$ Max. $K.E$ with which photoelectrons are emitted depends on the frequency of incident light.

$D.$ The emission of photoelectrons require a minimum threshold intensity of incident radiation.

$E.$ Max. K.E of the photoelectrons is independent of the frequency of the incident light.

Choose the correct answer from the options given below:

Which of the following statement is not correct

In a photoelectric effect experiment a light of frequency $1.5$ times the threshold frequency is made to fall on the surface of photosensitive material. Now if the frequency is halved and intensity is doubled, the number of photo electrons emitted will be: