Quantum Physics

Photoelectric effect provides the evidence for the ______ nature of radiation.

• wave

• particle

• dual

• electromagnetic

In the photoelectric effect, if the incident photons have a wavelength that is larger than the threshold wavelength, ______.

• there will be photoelectric current

• electrons will be ejected from the metal surface

• the kinetic energy of the ejected electrons increases

• no electrons will be emitted from the metal surface

The energy of a photon is directly proportional to its ______ and inversely proportional to its ______.

• intensity - speed

• wavelength - frequency

• frequency - wavelength

• intensity - wavelength

A particle of light is called a……

• Photon

• Photoelectron

• Proton

• Electron

The energy of photoelectrons emitted from a metal surface can be increased by

• using monochromatic, polarized light

• using light of longer wavelength

• using light of higher intensity

• using light of higher frequency

The following observation are made about the photoelectric effect:

1. No electron are emitted below the threshold frequency.

2. Above the threshold frequency the energy of electrons depends on the frequency of the light.

3. Increasing intensity increases the number of emitted electrons.

4. Energy of electromagnetic radiation is quantised.

Which of these observations can be explained by a Planck's Quantum theory of light?

• 1 and 3 only

• 2, 3 and 4 only

• 1, 2 and 4 only

• All of them

If the brightness of a beam of light increases without changing its colour, the ______ will increase.

• number of photons

• energy of the photons

• frequency of the light

• wavelength of the photons

What does the slope of the graph represent?

• Stopping potential

• Planck’s constant

• Mass of photon

• Speed of light

The graph shows maximum kinetic energy of emitted electrons against frequency of incident light for a number of different metals.

The threshold frequency is determined by:

• the x-intercept

• the y-intercept

• the gradient

• the area under the graph

The graph shows maximum kinetic energy of emitted electrons against frequency of incident light for a number of different metals.

The work function is determined by:

• the x-intercept

• the y-intercept

• the gradient

• the area under the graph