7.1.1 The Wave Nature of Light

Question 1

The Wave Nature of Light

Answer 1

• A quantum is an indivisible amount of something, such as light, energy, or matter.
• Light has wave properties, including wavelength, amplitude, velocity, frequency, and period.
• The electromagnetic spectrum is a continuum of wavelengths of electromagnetic radiation.

Question 2

note

Answer 2

• A quantum is an indivisible amount of something, such as light, energy, or matter. For example, the mass of sucrose is quantized. The smallest increment of mass that can be added or removed from a sample of sucrose is one molecule—anything less is no longer sucrose.
• Light has wave properties, including wavelength, amplitude, velocity, frequency, and period.
• The wavelength (λ) is the distance between one wave
  maximum and the next. The amplitude (A) is the height of the wave, and the velocity (v) is the rate at which a wave is propagating in a given direction. The frequency (ν) is the number of wave peaks that pass a point per unit time, and the period is the time interval between peaks of a wave.
• Wavelength (λ), frequency (ν), and velocity (v) are related by the equation v = V·λ . For light, the velocity is a constant, c = 3.00 x 10 8 m/s.
• The electromagnetic spectrum is a continuum of wavelengths of electromagnetic radiation. Visible light is a small subset of this spectrum, which also includes gamma radiation, x rays, ultraviolet radiation, infrared radiation, microwaves, and radio waves.

Question 3

Among other types of electromagnetic radiation, the sun radiates visible, infrared, and ultraviolet light. Which of these will take the longest to reach Earth through the near-vacuum of space?

Answer 3

All will take the same amount of time.

Question 4

Which label is most appropriate for the horizontal scale of this diagram of the electromagnetic spectrum?

Answer 4

Increasing wavelength

Question 5

Which of these best represents a quantum of the element oxygen?

Answer 5

a single atom of oxygen

Question 6

Blue light has a wavelength of about 475 nanometers. What is the period of light having this wavelength? (1 nanometer = 1 × 10^−9 meter)

Answer 6

1.58 × 10^−15 s

Question 7

A particular wavelength of red light is 1.5 times a particular wavelength of blue light. What is the relationship between the frequencies of these two waves?

Answer 7

νred = (0.67) • νblue

Question 8

Which of the following is not quantized?

Answer 8

numbers

Question 9

What is the mass (in grams) of one quantum of water? Assume a sample whose atoms consist entirely of isotopes of oxygen-16 and hydrogen-1.

Answer 9

2.992 × 10^−23 g

Question 10

The diagram below represents an electromagnetic wave.

Which of the following represents the wave after its frequency is doubled?

Answer 10

This diagram shows twice as many peaks as the original diagram in the same amount of space. Therefore, this wave has twice the frequency of the original wave. Notice that the wavelength of this wave is half that of the wavelength of the original wave. The frequency cannot be changed without also changing wavelength.

Question 11

A radio station broadcasts at a frequency of 107 megahertz. What is the wavelength of the radio waves broadcast by the station? (1 megahertz = 1 × 106 hertz)

Answer 11

2.80 m

Question 12

In general, visible light cannot be used to resolve an object smaller than the light’s wavelength. Suppose a bacterium has a diameter of 0.6 micron. What is the lowest frequency of light that could be used to resolve it? (1 micron = 1 × 10^−6 m)

Answer 12

5 × 10^14 s−1