CLASSICAL NOTES – 2020
TOPICS:
1. Waves
2. Electromagnetism
3. Radioactivity
4. Thermionic emission
5. Electronics
6. Elementary astronomy
7. Geophysics
Written by Geoffrey M Idebe (0688 082 089) Page 1
, TOPIC–1 WAVES
Wave: Is a progressive disturbance propagated from a point in a medium (matter)
on space without the movement of the points themselves.
OR Is a periodic disturbance that transfers energy from one point to another
For example, light, sound and water waves
Terms Used
1. Period: Is the time taken by the wave to repeat itself.
OR Is the time taken for the wave to complete one cycle.
It is represented by letter T. Its SI unit is second (s)
2. Amplitude: Is the maximum displacement of the wave from the equilibrium position.
It is represented by letter A. Its SI unit is meter (m).
3. Crest: Is the point of maximum positive displacement of the wave from
the equilibrium position
4. Trough: Is the point of maximum negative displacement of the wave from
the equilibrium position
5. Wavelength: Is the distance between two successive or adjacent crest troughs.
OR Is the distance travelled by the wave to complete one cycle
It represented by letter Lambda (λ)
Written by Geoffrey M Idebe (0688 082 089) Page 2
, 6. Frequency: Is the number of crests or troughs that pass a given point per unit time.
OR Is the number of cycles per unit time.
It is represented by letter f. Its SI unit is hertz (Hz).
1hertz (Hz) = 1per second (s-1)
𝟏
Then 𝒇 = , where T is a periodic time
𝑻
7. Wave velocity: Is the speed at which the wave moves through a medium
OR Is the displacement of the wave per unit time.
It is represented by letter v
Mathematically
𝒘𝒂𝒗𝒆𝒍𝒆𝒏𝒈𝒕𝒉 𝝀 𝟏
𝒔𝒑𝒆𝒆𝒅 (𝑽) = = = 𝝀 × = 𝝀 ×𝒇
𝒕𝒊𝒎𝒆 𝑻 𝑻
Therefore: 𝒗 =𝝀𝒇
Examples:
1. Sound waves have a frequency of 16 kHz. What is the periodic time for the
waves?
Soln:
Given: 𝒇 = 𝟏𝟔𝒌𝑯𝒛 = 𝟏𝟔 𝟎𝟎𝟎𝑯𝒛
𝟏 𝑰 𝟏
From: 𝒇 = →𝑻= = = 𝟎. 𝟎𝟎𝟎𝟎𝟔𝟐𝟓 𝒔
𝑻 𝒇 𝟏𝟔𝟎𝟎𝟎
2. A radio station transmits waves at a frequency of 95.6 MHz. What is the
wavelength of the waves transmitted? (c = 3.0 x 108 m/s)
Soln:
Given: 𝒇 = 𝟗𝟓. 𝟔𝑴𝑯𝒛 = 𝟗𝟓. 𝟔 𝒙 𝟏𝟎𝟔 𝑯𝒛, c = 3.0 x 108 m/s
𝟑.𝟎 𝒙𝟏𝟎𝟖
From: 𝒗 = 𝝀 𝒇 →
𝒗
𝝀=𝒇=
𝟗𝟓.𝟔 𝒙 𝟏𝟎𝟔
= 𝟑. 𝟏𝟒 𝒎
Class Activity – 1:1
1. From the diagram below, determine the amplitude, period and frequency of the
wave
ANS: Amplitude, A = 0.5m Period, T = 0.2 Frequency = 5Hz
2. From the diagram below, determine the wavelength and velocity of the wave,
frequency of the wave is 5Hz (ANS V = 10m/s)
Written by Geoffrey M Idebe (0688 082 089) Page 3
, 3. What is the amplitude and wave length of the wave in the diagram below?
ANS: A = 0.03m, Wavelength = 0.08 m
4. A periodic and repeating disturbance in a lake creates waves which emanate
outward from its source to produce circular wave patterns. If the frequency of the
source is 2.00 Hz and the wave speed is 5.00m/s then the distance between
adjacent wave crests is ___ meter.(ANS: Wavelength = 10 m)
5. Calculate the wavelength of red light in air if the frequency of red light is 4.3 x
1014 Hz, C = 3.0 X 108 (ANS: 6.98 x 10-7m)
6. A pendulum makes exactly 40 vibrations in 20.0 s. Its period is (ANS: 0.5 s)
7. If the frequency of a wave is doubled and if the speed remains constant, its
wavelength is ___ (ANS: halved.)
8. A wave whose speed in a snake is 4.4 m/s enters a second snakey. The
wavelength changes from 2.0 m to 3.0 m. The wave in the second snakey
travels at approximately ____. (ANS: 6.6 m/s.)
9. A 2.0-meter long rope is hanging vertically from the ceiling and attached to a
vibrator. A single pulse is observed to travel to the end of the rope in 0.50 s.
What frequency should be used by the vibrator to maintain three whole waves
in the rope? (ANS: 6.0 Hz)
10. Transverse stationary waves are set up in a long string using a suitable vibrator
of frequency 60 Hz. The average distance between successive nodal points is
measured to be 50 cm .Calculate the velocity of transverse waves in the string
ANS: V = 60 M/S
11. The distance between successive crests of water ripples in a ripple tank
experiment is 3.2 cm and their wave speed is 26 cm/s. Determine the
wavelength ,Frequency and period of the ripples ANS: f = 8.125 Hz, λ=3.2cm T=0.123 Hz
Written by Geoffrey M Idebe (0688 082 089) Page 4
TOPICS:
1. Waves
2. Electromagnetism
3. Radioactivity
4. Thermionic emission
5. Electronics
6. Elementary astronomy
7. Geophysics
Written by Geoffrey M Idebe (0688 082 089) Page 1
, TOPIC–1 WAVES
Wave: Is a progressive disturbance propagated from a point in a medium (matter)
on space without the movement of the points themselves.
OR Is a periodic disturbance that transfers energy from one point to another
For example, light, sound and water waves
Terms Used
1. Period: Is the time taken by the wave to repeat itself.
OR Is the time taken for the wave to complete one cycle.
It is represented by letter T. Its SI unit is second (s)
2. Amplitude: Is the maximum displacement of the wave from the equilibrium position.
It is represented by letter A. Its SI unit is meter (m).
3. Crest: Is the point of maximum positive displacement of the wave from
the equilibrium position
4. Trough: Is the point of maximum negative displacement of the wave from
the equilibrium position
5. Wavelength: Is the distance between two successive or adjacent crest troughs.
OR Is the distance travelled by the wave to complete one cycle
It represented by letter Lambda (λ)
Written by Geoffrey M Idebe (0688 082 089) Page 2
, 6. Frequency: Is the number of crests or troughs that pass a given point per unit time.
OR Is the number of cycles per unit time.
It is represented by letter f. Its SI unit is hertz (Hz).
1hertz (Hz) = 1per second (s-1)
𝟏
Then 𝒇 = , where T is a periodic time
𝑻
7. Wave velocity: Is the speed at which the wave moves through a medium
OR Is the displacement of the wave per unit time.
It is represented by letter v
Mathematically
𝒘𝒂𝒗𝒆𝒍𝒆𝒏𝒈𝒕𝒉 𝝀 𝟏
𝒔𝒑𝒆𝒆𝒅 (𝑽) = = = 𝝀 × = 𝝀 ×𝒇
𝒕𝒊𝒎𝒆 𝑻 𝑻
Therefore: 𝒗 =𝝀𝒇
Examples:
1. Sound waves have a frequency of 16 kHz. What is the periodic time for the
waves?
Soln:
Given: 𝒇 = 𝟏𝟔𝒌𝑯𝒛 = 𝟏𝟔 𝟎𝟎𝟎𝑯𝒛
𝟏 𝑰 𝟏
From: 𝒇 = →𝑻= = = 𝟎. 𝟎𝟎𝟎𝟎𝟔𝟐𝟓 𝒔
𝑻 𝒇 𝟏𝟔𝟎𝟎𝟎
2. A radio station transmits waves at a frequency of 95.6 MHz. What is the
wavelength of the waves transmitted? (c = 3.0 x 108 m/s)
Soln:
Given: 𝒇 = 𝟗𝟓. 𝟔𝑴𝑯𝒛 = 𝟗𝟓. 𝟔 𝒙 𝟏𝟎𝟔 𝑯𝒛, c = 3.0 x 108 m/s
𝟑.𝟎 𝒙𝟏𝟎𝟖
From: 𝒗 = 𝝀 𝒇 →
𝒗
𝝀=𝒇=
𝟗𝟓.𝟔 𝒙 𝟏𝟎𝟔
= 𝟑. 𝟏𝟒 𝒎
Class Activity – 1:1
1. From the diagram below, determine the amplitude, period and frequency of the
wave
ANS: Amplitude, A = 0.5m Period, T = 0.2 Frequency = 5Hz
2. From the diagram below, determine the wavelength and velocity of the wave,
frequency of the wave is 5Hz (ANS V = 10m/s)
Written by Geoffrey M Idebe (0688 082 089) Page 3
, 3. What is the amplitude and wave length of the wave in the diagram below?
ANS: A = 0.03m, Wavelength = 0.08 m
4. A periodic and repeating disturbance in a lake creates waves which emanate
outward from its source to produce circular wave patterns. If the frequency of the
source is 2.00 Hz and the wave speed is 5.00m/s then the distance between
adjacent wave crests is ___ meter.(ANS: Wavelength = 10 m)
5. Calculate the wavelength of red light in air if the frequency of red light is 4.3 x
1014 Hz, C = 3.0 X 108 (ANS: 6.98 x 10-7m)
6. A pendulum makes exactly 40 vibrations in 20.0 s. Its period is (ANS: 0.5 s)
7. If the frequency of a wave is doubled and if the speed remains constant, its
wavelength is ___ (ANS: halved.)
8. A wave whose speed in a snake is 4.4 m/s enters a second snakey. The
wavelength changes from 2.0 m to 3.0 m. The wave in the second snakey
travels at approximately ____. (ANS: 6.6 m/s.)
9. A 2.0-meter long rope is hanging vertically from the ceiling and attached to a
vibrator. A single pulse is observed to travel to the end of the rope in 0.50 s.
What frequency should be used by the vibrator to maintain three whole waves
in the rope? (ANS: 6.0 Hz)
10. Transverse stationary waves are set up in a long string using a suitable vibrator
of frequency 60 Hz. The average distance between successive nodal points is
measured to be 50 cm .Calculate the velocity of transverse waves in the string
ANS: V = 60 M/S
11. The distance between successive crests of water ripples in a ripple tank
experiment is 3.2 cm and their wave speed is 26 cm/s. Determine the
wavelength ,Frequency and period of the ripples ANS: f = 8.125 Hz, λ=3.2cm T=0.123 Hz
Written by Geoffrey M Idebe (0688 082 089) Page 4
