# Worksheet: Interference of Light Waves

In this worksheet, we will practice defining wave interference and describing the constructive and destructive interference of waves that are mutually in or out of phase.

Q1:

The two waves shown in the diagram have the same frequency and wavelength as each other, but with different initial displacements. If the two waves interfere, which of the other diagrams—(A), (B), (C), and (D)—best shows how the resultant wave compares to the two waves?  • A(C)
• B(A)
• C(B)
• D(D)

Q2:

The two waves shown in the diagram have the same frequency, wavelength, and initial displacement. If the two waves interfere, which of the other diagrams—(A), (B), (C), and (D)—best shows how the resultant wave compares to the two identical waves? • A(D)
• B(B)
• C(A)
• D(C)

Q3:

Two waves of the same frequency, and wavelength pass each other, traveling in opposite directions. Both waves have an amplitude of 1 cm. The waves interfere to produce a resultant wave. The diagram shows the displacement of points on the resultant wave at an instant in time. Is the interference of the two waves at point constructive or destructive?

• BConstructive

Is the interference of the two waves at point constructive or destructive?

• AConstructive
• BDestructive

Q4:

Which of the following statements correctly defines constructive interference?

• AConstructive interference of two waves occurs when the resultant wave has zero amplitude.
• BConstructive interference of two waves occurs when the resultant wave has an amplitude equal to the average of the amplitudes of the two waves.
• CConstructive interference of two waves occurs when the resultant wave has an amplitude equal to the sum of the amplitudes of the two waves.
• DConstructive interference of two waves occurs when the resultant wave has an amplitude equal to the difference of the amplitudes of the two waves.

Q5:

Which of the following statements correctly defines destructive interference?

• ADestructive interference of two waves occurs when the resultant wave has zero amplitude.
• BDestructive interference of two waves occurs when the resultant wave has an amplitude equal to the sum of the amplitudes of the two waves.
• CDestructive interference of two waves occurs when the resultant wave has an amplitude equal to the difference of the amplitudes of the two waves.
• DDestructive interference of two waves occurs when the resultant wave has an amplitude equal to the average of the amplitudes of the two waves.

Q6:

Two waves with the same wavelengths and frequencies as each other move in the same direction, with one wave leading the other by one whole wavelength. Is the interference between the waves constructive, destructive, or neither constructive nor destructive?

• ANeither constructive nor destructive
• BDestructive
• CConstructive

Q7:

Two waves with the same wavelength and frequency move in the same direction, with one wave leading the other by one whole wavelength. Is the interference between the waves constructive, destructive, or neither constructive nor destructive?

• ANeither constructive nor destructive
• BConstructive
• CDestructive

Q8:

Two waves of different wavelengths move toward each other, as shown in the diagram. Which of the other diagrams, (a), (b), (c), and (d), shows the result of the two waves interfering? • A(c)
• B(b)
• C(a)
• D(d)

Q9:

The diagram shows the wave fronts of two waves traveling in different directions. How many of its wavelengths has the horizontally traveling wave moved by at point ?

How many of its wavelengths has the diagonally traveling wave moved by at point ?

If the horizontal wave at point was to be combined with the diagonal wave at point , would the interference be constructive or destructive?

• AConstructive
• BDestructive

How many of its wavelengths has the horizontally traveling wave moved by at point ?

How many of its wavelengths has the diagonally traveling wave moved by at point ?

If the horizontal wave at point was to be combined with the diagonal wave at point , would the interference be constructive or destructive?

• BConstructive

How many of its wavelengths has the horizontally traveling wave moved by at point ?

How many of its wavelengths has the diagonally traveling wave moved by at point ?

If the horizontal wave at point was to be combined with the diagonal wave at point , would the interference be constructive or destructive?

• AConstructive
• BDestructive

Q10:

Two wave pulses on a string approach each other from opposite directions, as shown in the diagram. Which of the four resultant waves—i, ii, iii, and iv—most correctly shows the resultant of the two pulses? • Aiv
• Bii
• Ci
• Diii