Matter & Atoms

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)

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

If N₀ 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

1. N₀/16
2. N₀/8
3. N₀/4
4. N₀/2

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

1. 0 eV
2. 3.4 eV
3. 6.8 eV
4. 10.2 eV

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

1. 220 nm
2. 310 nm
3. 400 nm
4. 540 nm

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. 1.41 eV
2. 1.51 eV
3. 1.68 eV
4. 3.09 eV

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

1. 12.1 eV
2. 12.4 eV
3. 36.3 eV
4. 108.8 eV

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

If a source of power 4 kW produces 10²⁰ photons/second, the radiation belongs to a part of the spectrum called

1. microwaves
2. X rays
3. γ rays
4. ultraviolet rays

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

1. depends both on the intensity of the radiation and the metal used
2. depends on the nature of the metal used
3. depends on the intensity of the radiation
4. is the same for all metals and independent of the intensity of the radiation

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

1. Electrons
2. Protons
3. He²⁺
4. Neutrons

The emission at instant can be

1. 1, 2, 3, 4
2. 1, 2, 3
3. 2, 3
4. 4

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:

1. 4 : 1
2. 1 : 4
3. 5 : 4
4. 1 : 16