AP Physics: Electrons & Energy

A material is heated to 5,000 K and emits light in the visible spectrum. If the material were heated to 7,000 K instead, what changes would be seen?

• The graph would have bright peaks at several different wavelengths

• The graph would stay the same shape but peak at a smaller wavelength

• The graph would stay the same shape but peak at a larger wavelength

• The graph would be bright consistently across with dark bands of minima at different wavelengths

How much energy would it take to ionize an electron in the ground state?

• 1 eV

• 3 eV

• 7 eV

• 12 eV

Which transition would result in a photon with the largest wavelength?

• From -1 to -12

• From -3 to -7

• From -7 to -12

• From -1 to -3

Light is emitted by transitioning an electron form the 3rd to the second excited state of a hydrogen atom in the Bohr model. If the transition were from the n = 3 to the n = 1 level instead, the light emitted would have

• lower frequency

• longer wavelength

• higher energy

• larger amplitude

According to the Bohr theory, electrons in the the 4th energy level and eventually ending up in the ground state could produce a total of how many lines in the hydrogen spectra?

• 7

• 6

• 5

• 4

• 3

The approximate work-function of this material is

• 1.5 eV

• 2.0 eV

• 2.7 eV

• 4.0 eV

• 6.0 eV

The approximate cut-off frequency is of this material is

• 2.5 * 10¹⁴ Hz

• 3.5 * 10¹⁴ Hz

• -1.5 * 10¹⁴ Hz

• 6.63 * 10^-34 Hz

• 4.13 * 10¹⁵ Hz

What does the slope of this graph represent?

• The work-function of the material

• Planck's constant in eV-s

• the cut-off frequency of the material

• Planck's constant in J-s

• the kinetic energy of the electrons

In the photoelectric effect, a light of a given frequency shining on a metal causes electrons from that metal to be ejected. If the frequency of the light is kept constant while the intensity is increased:

• more electrons will be ejected

• fewer electrons will be ejected

• the same number of electrons will be ejected but with a higher speed for each electron

• the same number of electrons but with a lower speed

• the same number of electrons and those will require an increased stopping voltage to prevent a photocurrent

The maximum speed of the electrons emitted by a metal surface when it is illuminated by light depends on which of the following?

• I only

• III only

• I and II only

• II and III only

• all of the above