Quantum Mechanics | MCQs

Explanation

The photoelectric effect best explains the particle nature of light. 

Explanation

Electronic transitions occur when electrons jump between energy levels in an atom.

These transitions typically release photons in the infrared, visible, or ultraviolet regions — depending on the energy difference.

γ-radiations (gamma rays) are high-energy photons emitted from the nucleus, not from electronic transitions.

They are associated with nuclear reactions, not electronic energy level changes.

Explanation

The maximum kinetic energy (K.E.) of photoelectrons depends on the frequency of the incident light, not its intensity. 

According to Einstein's photoelectric equation:

K.E. = hf - φ

where hf is the energy of the photon, which depends on its frequency (f).

Explanation

The correct equation representing Heisenberg's uncertainty principle is A) Δx. Δp ≥ ħ/2. 

This equation relates the uncertainty in position (Δx) to the uncertainty in momentum (Δp),

Where "ħ" is the reduced Planck constant. 

Explanation

Explanation

Bohr's quantum condition states that the angular momentum of an electron in a circular orbit is quantized:

mvr = nh / 2π

where m is the mass of the electron,

v is the velocity,

r is the radius of the orbit,

n is the principal quantum number,

and h is Planck's constant.

Explanation

Energy of one photon (E) = hc / λ

h = 6.626 × 10^-34 Js

c = 3 × 10^8 m/s

λ = 4961 Å = 4961 × 10^-10 m

E = (6.626 × 10^-34 Js × 3 × 10^8 m/s) / (4961 × 10^-10 m)

= 4.007 × 10^-19 J

Number of photons required to do 1 J of work:

n = 1 J / (4.007 × 10^-19 J)

= 2.4961 × 10^18

Explanation

The energy required to excite an electron from the second orbit to the third orbit is:

ΔE = 13.6Z^2(1/4 - 1/9) eV

Given ΔE = 42.7 eV:

42.7 = 13.6Z^2(1/4 - 1/9)

Solving for Z:

Z = 4

Explanation

Explanation

The Fermi energy is the highest energy level that electrons occupy at absolute zero temperature.

Above this energy, states are empty, and below it, they are filled.