# Lesson Worksheet: The Huygens Wave Model Physics • 9th Grade

In this worksheet, we will practice describing the processes of propagation, reflection, refraction, and diffraction using the Huygens wave model.

Q1:

The diagram shows a plane wave traveling in a medium . The wave propagates as described by the Huygens wave model. The wave is incident at a boundary, beyond which there is a medium . Which of the arrows shown correctly represents the direction of the wave traveling in ? • AI
• BV
• CII
• DIV
• EIII

Q2:

The diagram shows a plane wave that is incident on a reflective surface. The wave propagates as described by the Huygens wave model. At an instant , the dashed pink line is tangential to the wave fronts of wavelets emitted from equally separated point sources on the reflective surface. The interval is the time taken for a wavelet to travel through four wavelengths of the plane wave. Which of the following is the time at which the first wavelet is emitted from the reflective surface? • A
• B
• C
• D
• E

Q3:

The diagram shows a plane wave that is incident on a reflective surface. The wave propagates as described by the Huygens wave model. At an instant , the dashed pink line is tangential to the wave fronts of wavelets emitted from equally separated point sources on the reflective surface. Which of the arrows shown correctly represents the direction of the plane wave reflected from the surface? • AI
• BIII
• CIV
• DV
• EII

Q4:

The diagram shows a plane wave that is incident on a reflective surface. The wave propagates as described by the Huygens wave model. The points A, B, C, and D are point sources of wavelets emitted from the reflective surface. How many wavelengths of the plane wave does the wave front of the wavelet that originates at point D travel to reach point H?

How many wavelengths of the plane wave does the wave front of the wavelet that originates at point B travel to reach point F?

The number of wavelengths of the plane wave that are traveled by the wave front of the wavelet that originates at point A to reach point E is . The number of wavelengths of the plane wave that are traveled by the wave front of the wavelet that originates at point C to reach point G is . What is the ratio of to ?

Q5:

The diagram shows a plane wave propagating, as described by the Huygens wave model. Which of the following features of the Huygens wave model corresponds to the part of the diagram labeled A?

• AA wavelet
• BA plane wave front
• CA point source
• DNone of these features

Which of the following features of the Huygens wave model corresponds to the part of the diagram labeled B?

• AA wavelet
• BA point source
• CA plane wave front
• DNone of these features

Which of the following features of the Huygens wave model corresponds to the part of the diagram labeled C?

• AA plane wave front
• BA point source
• CA wavelet
• DNone of these features

Q6:

The diagram shows a plane wave passing through a gap. The gap is perpendicular to the direction of propagation of the wave. Point sources on the wave front that is aligned with the opening of the gap from which the wave emerges are shown. A wavelet from one of these sources is shown propagating through a displacement . Which of the displacements shown in the diagram corresponds to the wavelength of the light waves emerging from the gap?

• A
• B
• C and
• DNeither nor

Which of the following most correctly correspond to what is represented in the diagram by the dashed lines?

• ARegions of strongly constructive interference of the wavelets from the wave front that is aligned with the opening of the gap from which the wave emerges
• BRegions of weakly destructive interference of the wavelets from the wave front that is aligned with the opening of the gap from which the wave emerges
• CRegions of strongly destructive interference of the wavelets from the wave front that is aligned with the opening of the gap from which the wave emerges
• DWave fronts of the wave that is aligned with the opening of the gap from which the wave emerges
• ERegions of weakly constructive interference of the wavelets from the wave front that is aligned with the opening of the gap from which the wave emerges

Q7:

A point source of a light wave is shown in the diagram. The light wave propagates as described by the Huygens wave model. The wave fronts of the wave are represented by black rings. Which of the following features of the Huygens wave model corresponds to the black dots shown in the diagram?

• AWavelets
• BWave fronts
• CPoint sources
• DNone of these features

Which of the following features of the Huygens wave model corresponds to the gray curves shown in the diagram?

• APoint sources
• BWavelets
• CWave fronts
• DNone of these features

In a time interval , the smaller wave front emitted from the central point source propagates to the position of the larger wave front. Which color ring correctly represents the position of the wave front of the wave emitted from the central point source after a time interval ?

• ARed
• BGreen
• CBlue
• DNone of these colors

Q8:

The diagram shows a plane wave traveling in a medium . The wave propagates as described by the Huygens wave theory. The wave is incident at a boundary, beyond which there is a medium . The wave is refracted as it passes into the medium . Which of the following diagrams correctly compares the propagation of wavelets in and , ignoring the directions of propagation? Wavelet propagation in is shown in blue and wavelet propagation in is shown in green.

• A • B • C In which medium is the wavelength of the wave longer?

• A
• B

Which of the following is the relationship between , the refractive index of , and , the refractive index of ?

• A
• B
• C