Test Session Chap#7: Waves and Vibrations (1st Year Physics)

Multiple Choice Questions (MCQs)

Short Answer Questions

Important Formulas

Wave Speed:

v = fλ

where v = wave speed

f = frequency

λ = wavelength

String Frequency:

f = (n/2L)√(T/μ)

where n = harmonic number

L = string length

T = tension

μ = mass per unit length

Doppler Effect:

f’ = f(v ± v₀)/(v ∓ vₛ)

where f’ = observed frequency

f = source frequency

v = speed of sound

v₀ = observer velocity

vₛ = source velocity

Beats:

f_beat = |f₁ – f₂|

where f_beat = beat frequency

f₁, f₂ = frequencies of two waves

Wave Speed Calculator

Frequency (f) in Hz:

Wavelength (λ) in m:

String Frequency Calculator

Harmonic number (n):

String length (L) in m:

Tension (T) in N:

Linear density (μ) in kg/m:

Detailed Answer Questions

Question 1 (5 marks)

A train sounds its horn before it sets off from the station and an observer waiting on the platform estimates its frequency at 1200 Hz. The train then moves off and accelerates steadily. Fifty seconds after departure, the driver sounds the horn again and the platform observer estimates the frequency of 1140 Hz. Calculate the train speed 50 s after departure. How far from the station is the train after 50 s. [Speed of sound = 340 ms⁻¹]

Question 2 (5 marks)

Define stationary waves. Show that frequencies of stationary waves in a stretched string are quantized.

Question 3 (5 marks)

Explain in detail experiment demonstrating stationary waves using microwaves.

Note: Answer any 2 questions. Each question carries 5 marks.

Your Score: 0 / 10