Waves
- A wave of frequency 100 Hz is sent along a string towards a fixed end. When this wave travels back after reflection, a node is formed at a distance of 10 cm from the fixed end of the string. The speeds of incident (and reflected) waves are
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As fixed end is a node, therefore, distance between two consecutive nodes
- λ - 10 cm. 2
λ = 20 cm = 0.2 m
As v - nλ ∴ v = 100 × 0.2 = 20 m/sCorrect Option: C
As fixed end is a node, therefore, distance between two consecutive nodes
- λ - 10 cm. 2
λ = 20 cm = 0.2 m
As v - nλ ∴ v = 100 × 0.2 = 20 m/s
- Which of the following equations represent a wave?
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y = A sin (at – bx + c) represents a wave, where a may correspond to ω and b may correspond to K.
Correct Option: C
y = A sin (at – bx + c) represents a wave, where a may correspond to ω and b may correspond to K.
- A standing wave is represented by y = Asin (100t) cos (0.01x), where y and A are in millimetre, t in seconds and x is in metre. Velocity of wave is
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The wave equation is y = Asin (ωt)cos (kx);
c = ω/k = 100/0.01 = 104 m/s.Correct Option: A
The wave equation is y = Asin (ωt)cos (kx);
c = ω/k = 100/0.01 = 104 m/s.
- A hospital uses an ultrasonic scanner to locate tumours in a tissue. The operating frequency of the scanner is 4.2 MHz. The speed of sound in a tissue is 1.7 km/s. The wavelength of sound in tissue is close to
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Frequency (n) = 4.2 MHz = 4.2 × 106 Hz and
speed of sound (v) = 1.7 km/s = 1.7 × 10³ m/s.
Wave length of sound in tissue(λ) = v = 1.7 × 10³ = 4 × 10- 4 m. n 4.2 × 106 Correct Option: A
Frequency (n) = 4.2 MHz = 4.2 × 106 Hz and
speed of sound (v) = 1.7 km/s = 1.7 × 10³ m/s.
Wave length of sound in tissue(λ) = v = 1.7 × 10³ = 4 × 10- 4 m. n 4.2 × 106
- The speed of a wave in a medium is 760 m/s. If 3600 waves are passing through a point in the medium in 2 min, then their wavelength is
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Speed of the wave (v) = 760 m/s; Number of waves = 3600 and time taken (t) = 2 min = 120 sec. Frequecny of waves
= 3600 = 30/sec 120
∴ wavelength of waves (λ)(n) = v = 760 = 25.3 m. n 30
[Alt : λ = ct/w , where c = velocity of wave
t = time in second
w = no. of waves]Correct Option: B
Speed of the wave (v) = 760 m/s; Number of waves = 3600 and time taken (t) = 2 min = 120 sec. Frequecny of waves
= 3600 = 30/sec 120
∴ wavelength of waves (λ)(n) = v = 760 = 25.3 m. n 30
[Alt : λ = ct/w , where c = velocity of wave
t = time in second
w = no. of waves]
