1
###
An electron from various excited states of hydrogen atom emit radiation

An electron from various excited states of hydrogen atom emit radiation to come to the ground state. Let λ_{n}, λ_{g} be the de Broglie wavelength of the electron in the n^{th} state and the ground state respectively. Let Λ_{n} be the wavelength of the emitted photon in the transition from the n^{th} state to the ground state. For large n, (A, B are constants)

2
###
If N0 is the original mass of the substance of half-life period

If N_{0} is the original mass of the substance of half-life period t_{1/2} = 5 years, then the amount of substance left after 15 years is

- N
_{0}/16 - N
_{0}/8 - N
_{0}/4 - N
_{0}/2

3
###
If 13.6 eV energy is required to ionize the hydrogen atom

If 13.6 eV energy is required to ionize the hydrogen atom, then the energy required to remove an electron from n = 2 is

- 0 eV
- 3.4 eV
- 6.8 eV
- 10.2 eV

4
###
The work function of a substance is 4.0 eV

The work function of a substance is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from this substance is approximately

- 220 nm
- 310 nm
- 400 nm
- 540 nm

5
###
The surface of a metal is illuminated with the light of 400 nm

The surface of a metal is illuminated with the light of 400 nm. The kinetic energy of the ejected photoelectrons was found to be 1.68 eV. The work function of the metal is (hc = 1240 eV.nm)

- 1.41 eV
- 1.51 eV
- 1.68 eV
- 3.09 eV

6
###
Energy required for the electron excitation in Li++

Energy required for the electron excitation in Li^{++} from the first to the third Bohr orbit is

- 12.1 eV
- 12.4 eV
- 36.3 eV
- 108.8 eV

7
###
If a source of power 4 kW produces 10^20 photons/second

If a source of power 4 kW produces 10^{20} photons/second, the radiation belongs to a part of the spectrum called

- microwaves
- X rays
- γ rays
- ultraviolet rays

8
###
According to Einstein’s photoelectric equation, the plot of the kinetic energy

According to Einstein’s photoelectric equation, the plot of the kinetic energy of the emitted photoelectrons from a metal vs the frequency of the incident radiation gives a straight line whose slope

- depends both on the intensity of the radiation and the metal used
- depends on the nature of the metal used
- depends on the intensity of the radiation
- is the same for all metals and independent of the intensity of the radiation

9
###
At a specific instant, emission of radioactive compound is deflected in a magnetic field

At a specific instant, emission of radioactive compound is deflected in a magnetic field. The compound can emit

- Electrons
- Protons
- He
^{2+} - Neutrons

The emission at instant can be

- 1, 2, 3, 4
- 1, 2, 3
- 2, 3
- 4

10
###
Half-lives of two radioactive elements A and B are 20 minutes and 40 minutes

Half-lives of two radioactive elements A and B are 20 minutes and 40 minutes, respectively. Initially, the samples have equal number of nuclei. After 80 minutes, the ratio of decayed numbers of A and B nuclei will be:

- 4 : 1
- 1 : 4
- 5 : 4
- 1 : 16

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