Question 1

Which experiment provided the first strong evidence that light behaves as a wave?

Accepted Answer

Young's double-slit experiment

Question 2

According to Planck's quantum hypothesis, the energy of a photon is given by which equation?

Accepted Answer

$$E = hf$$

Question 3

In the photoelectric effect, increasing the intensity (brightness) of the incident light will:

Accepted Answer

Increase the number of ejected electrons

Question 4

Which of the following best describes the result when low-frequency light shines on a metal surface in a photoelectric effect experiment?

Accepted Answer

No electrons are ejected, regardless of intensity

Question 5

Einstein explained the photoelectric effect by proposing that light consists of:

Accepted Answer

Discrete particles called photons

Question 6

Which of the following statements about wave–particle duality is correct?

Accepted Answer

Light can behave as both a wave and a particle, depending on the experiment

Question 7

In the double-slit experiment with very dim light, what pattern emerges on the photographic film after a long exposure?

Accepted Answer

An interference pattern of bright and dark fringes

Question 8

According to de Broglie, the wavelength associated with a particle is given by:

Accepted Answer

$$\lambda = \frac{h}{p}$$

Question 9

Which modern device relies on the wave nature of electrons to produce high-resolution images?

Accepted Answer

Electron microscope

Question 10

Heisenberg's uncertainty principle states that the product of the uncertainties in position and momentum is at least:

Accepted Answer

$$\hbar = \frac{h}{2\pi}$$

Question 11

Which of the following is a consequence of the uncertainty principle?

Accepted Answer

It is impossible to simultaneously know the exact position and momentum of a particle

Question 12

Which of the following best describes the concept of complementarity introduced by Niels Bohr?

Accepted Answer

Wave and particle properties are mutually exclusive but both necessary for a complete description

Question 13

A photon has a frequency $$f. $$What is its energy?

Accepted Answer

$$E = hf$$

Question 14

If the uncertainty in the energy of a system is $$\Delta E$$, and the uncertainty in the time interval is $$\Delta t$$, what is the minimum value of their product according to the uncertainty principle?

Accepted Answer

$$\Delta E \Delta t \geq \hbar$$

Question 15

Which of the following is NOT a prediction of quantum theory?

Accepted Answer

The position and momentum of a particle can be known exactly at the same time

Question 16

A metal surface is illuminated with light of frequency $$f$$ just above the threshold frequency. What happens if the frequency is doubled?

Accepted Answer

The kinetic energy of the ejected electrons increases

Question 17

Which of the following best explains why the uncertainty principle is negligible in macroscopic laboratory measurements?

Accepted Answer

Planck's constant is extremely small

Question 18

In the context of the photoelectric effect, what is the 'work function' of a metal?

Accepted Answer

The minimum energy required to remove an electron from the metal

Question 19

Which of the following statements about electron diffraction is correct?

Accepted Answer

Electrons can produce interference patterns similar to light

Question 20

A beam of monochromatic light passes through two slits and forms an interference pattern. If the light intensity is reduced so that only one photon passes through at a time, what is observed after a long exposure?

Accepted Answer

A double-slit interference pattern

Chapter 31: Light Quanta – Quantum Theory and the Nature of Light

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