Dual Nature of Radiation and Matter quiz

Photoelectric current is directly proportional to:

The stopping potential depends on:

Einstein's photoelectric equation is:

The rest mass of a photon is:

The de Broglie wavelength of a particle of momentum p is:

Which metal has the lowest work function among these?

The momentum of a photon of energy E is:

If the frequency of incident light is increased (above threshold), the maximum kinetic energy of photoelectrons:

Photoelectric emission begins after a time lag of about:

The de Broglie wavelength of an electron accelerated through V volts is approximately:

Why does the photoelectric current saturate at high collector potential? (2 marks)

Why is no photoelectric emission observed below the threshold frequency however intense the light? (2 marks)

Why do photoelectrons have a range of kinetic energies from zero to a maximum? (2 marks)

An electron and a proton have the same de Broglie wavelength. Which has more kinetic energy? (2 marks)

What is the effect on stopping potential if the intensity of light is doubled at the same frequency? (2 marks)

Name two types of electron emission other than photoelectric emission. (2 marks)

Why are alkali metals suitable for photoelectric emission with visible light? (2 marks)

Write the relation between the de Broglie wavelength and kinetic energy of a particle of mass m. (2 marks)

What does the slope of the stopping potential versus frequency graph represent? (2 marks)

Why is the wave nature of matter not observed in daily life? (2 marks)

Calculate the energy (in eV) and momentum of a photon of wavelength 600 nm (h = 6.63 x 10^-34 J s). (3 marks)

Light of wavelength 200 nm falls on a metal of work function 4.2 eV. Find the maximum kinetic energy of photoelectrons and the stopping potential (hc = 1240 eV nm). (3 marks)

Find the de Broglie wavelength of an electron with kinetic energy 120 eV (m = 9.1 x 10^-31 kg, h = 6.63 x 10^-34 J s). (3 marks)

The stopping potential in an experiment is 1.5 V. Find the maximum kinetic energy and the maximum speed of the photoelectrons (m = 9.1 x 10^-31 kg). (3 marks)

The threshold wavelength of a metal is 300 nm. Find its work function in eV (hc = 1240 eV nm). Will light of 400 nm cause emission? (3 marks)

Read the passage and answer the questions. Automatic doors in malls use a photocell. A beam of light falls on a photosensitive surface, producing a current. When a person blocks the beam, the current stops and the door opens. (i) Which effect is used? (ii) Why must the light have a frequency above a certain value? (iii) What happens to the current if a brighter light of the same frequency is used? (5 marks)

Read the passage and answer the questions. A student shines red light (700 nm) of high intensity and violet light (400 nm) of low intensity on a sodium surface (work function 2.3 eV). (i) Find the photon energies (hc = 1240 eV nm). (ii) Which light causes emission? (iii) Explain why intensity alone does not matter. (5 marks)

Read the passage and answer the questions. An electron microscope uses electrons accelerated through 50 kV to observe objects much smaller than those visible with an optical microscope. (i) Find the de Broglie wavelength of the electrons (ignore relativity). (ii) Why does a smaller wavelength give better resolution? (iii) What property of electrons is used? (5 marks)

Read the passage and answer the questions. In an experiment, the photocurrent was measured for light of the same frequency at three intensities. The stopping potential was the same in all cases, but the saturation current increased with intensity. (i) Why is the stopping potential the same? (ii) Why does saturation current increase? (iii) Draw the graph. (5 marks)

Read the passage and answer the questions. Solar sails are proposed for spacecraft because sunlight exerts a small pressure: each photon carries momentum. (i) Write the expression for the momentum of a photon. (ii) Find the momentum of a photon of 500 nm. (iii) Why is a reflecting sail better than an absorbing one? (5 marks)

Describe the experimental study of the photoelectric effect with a labelled diagram, and explain the effects of intensity, potential and frequency with graphs. (6 marks)

Write Einstein's photoelectric equation and use it to explain the laws of photoelectric emission. Why did the wave theory fail? (6 marks)

State de Broglie's hypothesis and derive an expression for the de Broglie wavelength of an electron accelerated through a potential difference V. (6 marks)

Draw and explain graphs of photocurrent against collector potential for different intensities and frequencies. (6 marks)

Draw the graph of stopping potential against frequency for two metals and explain how Planck's constant and work functions are determined from it. (6 marks)