Review - Waves and Light
Modified True/False
Indicate whether the sentence or statement is true or false. If false, change the identified word or
phrase to make the sentence or statement true.
____
1. A wave ray indicates the direction of energy propagation for a wave.
_________________________
____
2. As water waves enter a deeper medium, they speed up and their wavelength shortens.
_________________________
____
3. The angle of incidence equals the angle of refraction. _________________________
____
4. The angle of incidence can be measured between the incident wave front and the boundary.
_________________________
____
5. Total internal reflection occurs when the incident angle is equal to the critical angle.
_________________________
____
6. As the size of an opening decreases, the amount of diffraction increases.
_________________________
____
7. Higher frequencies of sound bend through a doorway more easily.
_________________________
____
8. Michelson's interferometer was used to disprove the existence of an “ether” filling all of
space. _________________________
____
9. Waves of longer wavelength experience more diffraction than those of shorter wavelength.
_________________________
____ 10. For diffraction to be observable, the slit width w must be greater than or equal to the
wavelength . _________________________
____ 11. Destructive interference occurs when the resultant waveform has a smaller amplitude than
each individual wave. _________________________
____ 12. Nodal lines occur at points of continual constructive interference.
_________________________
____ 13. Decreasing the wavelength of the sources causes nodal lines in a two-point source
interference pattern to move closer together. _________________________
____ 14. The difference in path lengths from a point on a given nodal line to the two sources in a twopoint source interference pattern is directly proportional to the wavelength of the sources.
_________________________
Review - Waves and Light
____ 15. It is generally accepted that light exhibits only wave properties.
______________________________
____ 16. Christiaan Huygens was a strong supporter of the particle theory of light.
_________________________
____ 17. The wave theory of light was superior in explaining the phenomenon of diffraction.
_________________________
____ 18. Young’s double-slit experiment was designed to illustrate that light exhibits interference
patterns. _________________________
____ 19. In light, longer wavelengths refract less than shorter wavelengths.
_________________________
____ 20. The wave theory of light must be used to properly explain dispersion.
_________________________
Completion
Complete each sentence or statement.
21. When creating water waves in a ripple tank, the ____________________ appear as bright
areas on the screen below.
22. When the wavelength of a wave ____________________, the amount of noticeable
diffraction increases.
23. When generating a two-point source interference pattern in a ripple tank, increasing the
frequency of the sources causes the wavelength to ____________________.
24. In Young’s double-slit experiment, a(n) ____________________ is produced at the centre of
the pattern.
25. The observation that nodal lines are more spaced out for red light than for blue light
indicates that red light has a(n) ____________________ wavelength than blue light.
26. The bending of a wave due to changing speed is called ____________________.
27. The bending of a wave around corners or through openings is called
____________________.
28. Light that is composed of a single colour, or wavelength, is called ____________________.
Review - Waves and Light
29. ____________________ defines the mathematical relationship between the angles of
incidence and refraction.
30. ____________________ interference occurs when the resultant waveform has a larger
amplitude than each individual wave.
31. Nodal lines in a two-point source interference pattern have a ____________________ shape.
32. The “corpuscular” theory of light was most strongly supported by ____________________.
33. The sharpness of shadows supports the property of light referred to as
______________________________.
34. A student observes white light entering a triangular prism and emerging in its spectral
colours on the other side. This phenomenon is called ____________________.
35. Red light bends least. According to Snell’s law, the wavelength of red light is
____________________ that of blue light.
Short Answer
1. Young’s experiment was instrumental in supporting Huygens’ wave theory of light.
Explain which two conditions Young satisfied in his experiment that were not adequately done
before. Describe how he achieved these two conditions.
2. The diagram shown below illustrates the possible paths followed by a light ray as it enters
a lens (n = 1.56) covered with a thin coating (n = 1.25). If the thin coating has a thickness of,
what type of interference occurs with rays 3 and 4.
Explain your answer.
3. Two water taps, closely separated, randomly drip into a sink that is half filled with water.
Each water droplet acts as a source for a circular wavefront. Even though there are two
Review - Waves and Light
sources continually creating water waves, no interference pattern is noticed. What two
conditions necessary to produce visible interference have not been met?
4. An astute student performs Young’s double slit experiment in water (nwater = 1.33) and
observes an interference pattern. The student then performs an identical experiment in flint
glass (nglass = 1.66) using the same equipment and distances. What changes would be noticed
in the interference pattern?
Problems
1. A two-point source interference pattern is generated in a swimming pool. A piece of
styrofoam, located on the second nodal line, is 12.0 m from one source and 20.0 m from the
other source. One wave crest takes 2.0 s to travel the 35.0 m width of the pool. Find the
speed, wavelength, and frequency of the waves.
2. Blue light with a wavelength of 475 nm is passed through a double slit with a separation
of 22.6 mm. What is the maximum number of nodal lines visible in the entire pattern?
3. Light travels in water at three-quarters the speed it attains in air. If the angle of incidence
in air were 10.0°, what would be the angle in water, according to particle theorist.
4. A laser emitting 632.8 nm illuminates a double slit. A screen is positioned 2.00 m from
the slits. Interference fringes are observed with a separation of 1.0 cm.
a) Determine the separation of the slits.
b) Determine the angle of the first-order dark fringes.
5. In a double-slit experiment, blue light of wavelength 4.60 x 10² nm gives a second order
maximum at a certain location P on the screen. What wavelength of visible light have a
minimum at P?
6. In young’s experiment while using a source of light of wavelength 5000 x10−10 m, the
fringe width obtained is 0.6 cm. If the distance between the screen and slit is reduced to half,
what should be the wavelength of the source to get fringes 0.4 cm wide?
Review - Waves and Light
7. A water wave in a ripple tank travels from a shallow to a deep region. The wavelength and
speed in the shallow region are 2.5 cm and 5.0 cm/s, respectively. If the wavelength in the
deep region is 6.0 cm, find
(a) The relative index of refraction from shallow to deep water
(b) The speed of the wave in the deep water.
8. A water wave travels from region 1, where the wavelength is 7.5 cm and the angle of
incidence is 45o, into region 2 where the angle of refraction is 25o. What is the wavelength in
region 2?
9. A student performs Young's doublescreen is placed 2.50 m from the centre of the sources such that a point on the fifth nodal line
is 37.5 cm from the centre of the interference pattern. Find the wavelength of the light used
and identify its colour.
Review - Waves and Light
Solutions:
Modified True/False
Indicate whether the sentence or statement is true or false. If false, change the identified word or
phrase to make the sentence or statement true.
__T_ 1. A wave ray indicates the direction of energy propagation for a wave.
_________________________
___F_ 2. As water waves enter a deeper medium, they speed up and their wavelength shortens.
___LENGTHENS/INCREASES___
__F__ 3. The angle of incidence equals the angle of refraction.
____REFLECTION _____________________
__T__ 4. The angle of incidence can be measured between the incident wave front and the boundary.
_________________________
__F__ 5. Total internal reflection occurs when the incident angle is equal to the critical angle.
_________IS GREATER THAN________________
___T_ 6. As the size of an opening decreases, the amount of diffraction increases.
_________________________
___F_ 7. Higher frequencies of sound bend through a doorway more easily.
____LOWER_____________________
_T___ 8. Michelson's interferometer was used to disprove the existence of an “ether” filling all of
space. _________________________
__T__ 9. Waves of longer wavelength experience more diffraction than those of shorter wavelength.
_________________________
__F__10. For diffraction to be observable, the slit width w must be greater than or equal to the
wavelength. ______LESS THAN OR EQUAL TO___________________
__T__11. Destructive interference occurs when the resultant waveform has a smaller amplitude than
each individual wave. _________________________
__F__12. Nodal lines occur at points of continual constructive interference. ______DESTRUCTIVE
INTERFERENCE___________________
__T__13. Decreasing the wavelength of the sources causes nodal lines in a two-point source
interference pattern to move closer together. _________________________
Review - Waves and Light
__T__14. The difference in path lengths from a point on a given nodal line to the two sources in a twopoint source interference pattern is directly proportional to the wavelength of the sources.
_________________________
__F__15. It is generally accepted that light exhibits only wave properties.
BOTH WAVE AND PARTICLE PROPERTIES ______________________
_F___16. Christiaan Huygens was a strong supporter of the particle theory of light.
WAVE THEORY_______________________
__T__17. The wave theory of light was superior in explaining the phenomenon of diffraction.
_________________________
_F___18. Young’s double-slit experiment was designed to illustrate that light exhibits interference
patterns. DIFFRACTION_________________________
__T__19. In light, longer wavelengths refract less than shorter wavelengths.
_________________________
__T__20. The wave theory of light must be used to properly explain dispersion.
_________________________
Completion
Complete each sentence or statement.
21. When creating water waves in a ripple tank, the ____CRESTS________________ appear as
bright areas on the screen below.
22. When the wavelength of a wave _____INCREASES_______, the amount of noticeable
diffraction increases.
23. When generating a two-point source interference pattern in a ripple tank, increasing the
frequency of the sources causes the wavelength to _DECREASE________________.
24. In Young’s double-slit experiment, a(n) _ANTINODAL LINE/MAXIMUM_ is produced at
the centre of the pattern.
25. The observation that nodal lines are more spaced out for red light than for blue light
indicates that red light has a(n) _____LONGER_______________ wavelength than blue
light.
26. The bending of a wave due to changing speed is called
___REFRACTION_________________.
27. The bending of a wave around corners or through openings is called
__DIFFRACTION__________________.
Review - Waves and Light
28. Light that is composed of a single colour, or wavelength, is called
_____MONOCHROMATIC_______________.
29. _____SNELL’S LAW_______________ defines the mathematical relationship between the
angles of incidence and refraction.
30. ____CONSTRUCTIVE________________ interference occurs when the resultant
waveform has a larger amplitude than each individual wave.
31. Nodal lines in a two-point source interference pattern have a ___HYPERBOLIC_____
shape.
32. The “corpuscular” theory of light was most strongly supported by _ISSAC
NEWTON_______.
33. The sharpness of shadows supports the property of light referred to as RECTILINEAR
PROPOGATION.
34. A student observes white light entering a triangular prism and emerging in its spectral
colours on the other side. This phenomenon is called
____DISPERSION________________.
35. Red light bends least. According to Snell’s law, the wavelength of red light is _LONGER
THAN __ that of blue light.
SHORT ANSWERS:
1. - In order to see a stationary interference pattern, the phase of the two sources must be
constant, and the two narrow sources close together.
- By using a single bulb and two very narrow pinholes placed close together, Young was able to
satisfy both of these conditions, allowing a stationary diffraction pattern to be observed
2. Constructive interference occurs between the rays. Since ray 3 passes straight through, its
phase is unchanged. Ray 4 is reflected from a more dense surface, so its phase is inverted when it
reflects from the lens surface, but not inverted when it reflects from the air. Since ray 4 has
travelled a total of half a wavelength farther, the two rays are in opposite phase; however, the
extra inversion of wave 4 brings them back into phase. Hence, constructive interference occurs.
3. The sources are not in phase since they are randomly dripping.
The sources are not likely producing waves of the same frequency and wavelength.
Review - Waves and Light
4. Since the speed of light is slower in flint glass than in water, the wavelength of the source would
decrease. Shorter wavelengths diffract less and, thus, the diffraction pattern seen would be less
spread
out (i.e., the average spacing between bright fringes would decrease).
PROBLEMS:
Review - Waves and Light
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Q 7.
(a)
The relative index of refraction from shallow to deep water is 0.42.
(b)
The speed of the wave in the deep water is 12 cm/s.
Review - Waves and Light
Q 8.
The wavelength in region 2 is 4.5 cm.
Q9.
Review - Waves and Light
The colour used was red with a wavelength of 7.20 x 10-7 m.