Question

33a) Light falling on a metal surface causes electrons to be emitted from the metal by the photoelectric effect. As we increase the frequency of this light but keep its intensity the same.

A) the number of electrons emitted from the metal increases.

B) the maximum speed of the emitted electrons always remains the same.

C) the maximum speed of the emitted electrons is inversely proportional to the increase in the frequency of the incident light.

D) the number of electrons emitted from the metal does not change.

E) the number of electrons emitted from the metal is inversely proportional to the increase in the frequency of the incident light.

b) Which of the following statement about a typical atomic nucleus is correct?

A) The number of neutrons is equal to the number of protons.

B) It contains protons, neutrons, and neutrinos.

C) It usually contains more protons than neutrons.

D) It has a typical radius on the order of 10^-15 m.

E) It has a typical radius on the order of 10^-10 m.

c) A certain atomic nucleus containing 50 nucleons has a density ρ. If another nucleus contains 150 nucleons, its density will be closest to

A) 3ρ.

B) 3^2.3ρ = 2.08ρ.

C) 3^1/3ρ = 1.44ρ.

D) 3^1/2ρ = 1.73ρ.

E) ρ.

Answer 1

33a. The number of electrons emiited from a metal does not depend on the frequency of light depends on it. It depends on intensity of falling light.

Therefore number of particles emitted from metal will remain same.

With increase in frequency, kinetic energy of electrons emitted from metal also increases.

Only option D is correct.

33b). The number of neutron is equal to number of proton only for small size atoms. As the size of atom increases number of neutrons is always higher than number of protons for better stability. Statement A is not generally true. Statement C is not true

Nucleus cantains only proton and neutrons. Statement B is not true.

Nucleus typical radius is 10^-15. Statement D is true.

Statement E is not true.

33c. Density of a nucleus is a constant. It doesn't change with chamge in number of nucleons. Therefore density will remain p. Only option E is correct.