Q: A certain light source emits photons with a wavelength of $$400 \ \mathrm{nm}. $$What is the energy of one photon in joules? ($$h = 6.626 \times 10$$^{-34}$$ \ \mathrm{J \cdot s}$$, $$c = 3.00 \times 10^8$ \ \mathrm{m/s})$$

$$4.97 \times 10$$^{-19}$$ \ \mathrm{J}$$

Q: If the energy of a photon is $$2.11 \times 10^3$ \ \mathrm{kJ/mol}$$, what is the wavelength (in nm) of the light? ($$h = 6.626 \times 10$$^{-34}$$ \ \mathrm{J \cdot s}$$, $$c = 3.00 \times 10^8$ \ \mathrm{m/s}$$, $$1 \ \mathrm{mol} = 6.022 \times 10$$^{23}$$ photons)

$$5.67 \times 10^1$ \ \mathrm{nm}$$

Question 1

Which of the following best explains why the photoelectric effect could not be explained by classical wave theory?

Accepted Answer

Classical theory predicted that increasing light intensity, regardless of frequency, would always eject electrons.

Question 2

A metal has a work function $$\phi of$$ $$2.5 \ \mathrm{eV}. If $$light of frequency $$
u is $$shone on the metal and $$h
u = 3.0 \ \mathrm{eV}$$, what is the maximum kinetic energy of the ejected electrons?

Accepted Answer

$$0.5 \ \mathrm{eV}$$

Question 3

Which equation correctly relates the energy of a photon to its frequency?

Accepted Answer

$$E = h
u$$

Question 4

A certain light source emits photons with a wavelength of $$400 \ \mathrm{nm}. $$What is the energy of one photon in joules? ($$h = 6.626 	imes 10$$^{-34}$$ \ \mathrm{J \cdot s}$$, $$c = 3.00 	imes 10^8$ \ \mathrm{m/s})$$

Accepted Answer

$$4.97 	imes 10$$^{-19}$$ \ \mathrm{J}$$

Question 5

Which of the following statements about black body radiation is correct?

Accepted Answer

The peak wavelength of emission shifts to shorter wavelengths as temperature increases.

Question 6

The Rydberg formula for the hydrogen emission lines is $$\dfrac{1}{\lambda} = R_H \left( \dfrac{1}{n_1$^2} - \dfrac{1}{n_2$^2} \right). $$What does $$n_2$$ represent in this equation?

Accepted Answer

The principal quantum number of the higher energy level.

Question 7

According to the Bohr model, what happens when an electron in a hydrogen atom moves from $$n=3 to$$ $$n=2$$?

Accepted Answer

A photon is emitted with energy equal to the difference between the two energy levels.

Question 8

Which of the following best describes why atomic emission spectra are unique for each element?

Accepted Answer

Each element has a unique set of allowed energy levels for its electrons.

Question 9

A scientist observes that increasing the intensity of light below the threshold frequency does not cause electrons to be ejected from a metal surface. What does this observation support?

Accepted Answer

The energy of photons depends on their frequency, not intensity.

Question 10

If the energy of a photon is $$2.11 	imes 10^3$ \ \mathrm{kJ/mol}$$, what is the wavelength (in nm) of the light? ($$h = 6.626 	imes 10$$^{-34}$$ \ \mathrm{J \cdot s}$$, $$c = 3.00 	imes 10^8$ \ \mathrm{m/s}$$, $$1 \ \mathrm{mol} = 6.022 	imes 10$$^{23}$$ photons)

Accepted Answer

$$5.67 	imes 10^1$ \ \mathrm{nm}$$

Question 11

Which of the following is a correct statement about the quantization of energy in the Bohr model?

Accepted Answer

Electrons can only occupy certain discrete energy levels.

Question 12

The angular momentum of an electron in the Bohr model is given by $$L = n \dfrac{h}{2\pi}. $$What does $$n$$ represent?

Accepted Answer

The principal quantum number (an integer).

Question 13

Which of the following best describes the relationship between wavelength ($$\lambda) $$and frequency ($$
u) of $$electromagnetic radiation?

Accepted Answer

$$c = \lambda 
u$$

Question 14

A hospital uses ultraviolet light to sterilize equipment. Why is UV light effective for this purpose, based on its photon energy?

Accepted Answer

UV photons have enough energy to break chemical bonds in microorganisms.

Question 15

Which of the following is a real-world application of the photoelectric effect?

Accepted Answer

Solar panels converting sunlight into electricity.

Question 16

If the frequency of incident light is doubled, what happens to the energy of each photon?

Accepted Answer

It doubles.

Question 17

Which of the following best explains why the Bohr model is not a fully accurate physical model for atoms?

Accepted Answer

It assumes electrons move in fixed circular orbits, which is not supported by quantum mechanics.

Question 18

A sodium street lamp emits light at $$\lambda = 589 \ \mathrm{nm}. $$What is the energy of one photon of this light? ($$h = 6.626 	imes 10$$^{-34}$$ \ \mathrm{J \cdot s}$$, $$c = 3.00 	imes 10^8$ \ \mathrm{m/s})$$

Accepted Answer

$$3.37 	imes 10$$^{-19}$$ \ \mathrm{J}$$

Question 19

Which of the following is true about the intensity of electromagnetic radiation?

Accepted Answer

It is proportional to the number of photons per unit time.

Quantum Theory of Light and Atomic Spectra: Blackbody Radiation, Photoelectric Effect, and the Bohr Model

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