Modern Physics - Quantum Mechanics - SS2 Physics Past Questions and Answers - page 2
Which of the following best describes the photoelectric effect?
The emission of light by a material when exposed to electromagnetic radiation.
The emission of electrons from a material when exposed to electromagnetic radiation.
The absorption of light by a material resulting in the increase of its temperature.
The scattering of light by a material leading to the change in its direction.
According to the photon model of light, light is composed of particles called:
Electrons.
Protons.
Photons.
Neutrons.
Which of the following properties of light is explained by the photon model?
Interference.
Diffraction.
Reflection.
Particle-like behaviour.
The energy of a photon is directly proportional to its:
Amplitude.
Frequency.
Wavelength.
Speed.
In the photoelectric effect, increasing the intensity of light while keeping the frequency constant will:
Increase the number of emitted electrons.
Decrease the number of emitted electrons.
Have no effect on the number of emitted electrons.
Change the colour of the emitted light.
The threshold frequency for a certain metal is 5.0 × 1014 Hz. If light with a frequency of 6.0 × 1014 Hz is incident on the metal, calculate the kinetic energy of the emitted electrons. The work function of the metal is 4.0 eV.
To calculate the kinetic energy of the emitted electrons, we first need to determine if the incident light has enough energy to overcome the work function of the metal. If the frequency of the light is greater than or equal to the threshold frequency, it can emit electrons. In this case, the frequency (6.0 × 1014 Hz) is greater than the threshold frequency (5.0 × 1014 Hz), so electrons will be emitted.
The energy of a photon can be calculated using the equation: E = hf, where E is the energy, h is Planck's constant (6.63 × 10-34 J·s), and f is the frequency.
E = (6.63 × 10-34 J·s) × (6.0 × 1014 Hz) = 3.98 × 10-19 J
The kinetic energy of the emitted electrons can be calculated by subtracting the work function from the energy of the incident photons:
Kinetic energy = E - Work function
Kinetic energy = (3.98 × 10-19 J) - (4.0 eV × 1.6 × 10-19 J/eV)
= -2.88 × 10-20 J
Note: The negative sign indicates that the electrons have lost energy, which is consistent with the emission of electrons in the photoelectric effect.
A metal surface is irradiated with light of wavelength 500 nm. If the work function of the metal is 2.0 eV, calculate the maximum kinetic energy of the emitted electrons.
To calculate the maximum kinetic energy of the emitted electrons, we need to convert the given wavelength to frequency using the formula: f = c / λ, where f is the frequency, c is the speed of light (3.0 × 108 m/s), and λ is the wavelength.
f = (3.0 × 108 m/s) / (500 × 10-9 m) = 6.0 × 1014 Hz
Now, we can calculate the energy of the incident photons using the formula: E = hf.
E = (6.63 × 10-34 J·s) × (6.0 × 1014 Hz) = 3.98 × 10-19 J
The maximum kinetic energy of the emitted electrons can be calculated by subtracting the work function from the energy of the incident photons:
Kinetic energy = E - Work function
Kinetic energy = (3.98 × 10-19 J) - (2.0 eV × 1.6 × 10-19 J/eV)
= 1.38 × 10-19 J
In the electron diffraction experiment, electrons are passed through a narrow slit and directed at a screen with two slits. What phenomenon is observed?
Interference
Reflection
Refraction
Absorption
The diffraction pattern observed in the electron diffraction experiment is similar to the diffraction pattern observed for which type of waves?
Electromagnetic waves
Sound waves
Mechanical waves
Transverse waves
The wavelength of electrons used in the electron diffraction experiment can be calculated using:
De Broglie's equation
Planck's equation
Einstein's equation
Newton's equation