# Speed in a Medium

## Trending Questions

**Q.**

Light is an electromagnetic wave. Its speed in vacuum is given by the expression

√μ0e0

√μ0e0

√e0μ0

1√μ0e0

**Q.**A rope of uniform mass m and length L is hanging from a support. A block of mass M is attached to the rope at the lower end. If a transverse pulse is produced at the lower end, find the time taken by the pulse to reach the upper end.

- 2√Lg[√(1+Mm)−√Mm]
- 32√Lg[√(2+Mm)−√Mm]
- 32√Lg[√(1+Mm)−√Mm]
- √Lg[√(1+Mm)−√Mm]

**Q.**An observer standing near the sea shore observes 54 waves per minute. If the wavelength of the water wave is 10 m then the velocity of water wave is

- 540 ms
^{-1} - 5.4 ms
^{-1} - 0.184 ms
^{-1} - 9 ms
^{-1}

**Q.**A uniform rope of length L and mass m1 hangs vertically from a rigid support. A block of mass m2 is attached to the free end of the rope. A transverse pulse of wavelength λ1 is produced at the lower end of the rope. The wavelength of the pulse when it reaches the top of the rope is λ2. The ratio λ2λ1 is

- √m1+m2m2
- √m1m2
- √m1+m2m1
- √m2m1

**Q.**

Both the strings, shown in figure, are made of same material and have same cross-section. The pulleys are light. The wave speed of a transverse wave in the string AB is v1 and in CD it is v2. Then v1v2 is

1

2

**Q.**If the frequency of a wave is increased by 25% in the same medium. The change in its wavelength will be

- increase of 20%
- decrease of 20%
- increase of 25%
- decrease of 25%

**Q.**

The linear density of a vibrating string is 10−4kg/m. A transverse wave is propagating on the string, which is described by the equation y = 0.02 sin (x + 30 t), where x and y are in meters and time t in seconds. Then tension in the string is

0.09 N

3.6 N

0.36 N

0.9 N

**Q.**

A string of length 20 cm and linear mass density 0.40 g cm−1 is fixed at both ends and is kept under a tension of 16 N. A wave pulse is produced at t = 0 near an end as shown in figure (15-E3), which travels towards the other end. (a) When will the string have the shape shown in the figure again ? (b) Sketch the shape of the string at a time half of that found in part (a).

**Q.**Speed of sound in a gas at 27∘C is 360 m/s. Its speed at 37∘ C is

- 366 m/s
- 372 m/s
- 363 m/s
- 360 m/s

**Q.**Transverse waves travel with a speed of 40 m/s in a string under a tension of 12 N. What tension is required for a wave speed of 60 m/s in the same string?

- 25 N
- 29 N
- 27 N
- 21 N

**Q.**Under standard conditions the gas density is 1.3 mgcm3 and the velocity of sound propagation in it is 330 ms, then the number of degrees of freedom of gas is.

**Q.**

What is the relation between frequency and wavelength?

**Q.**A wire is 4 m long and has a mass of 0.2 kg. The wire is kept horizontally. A transverse pulse is generated by plucking one end of the taut (tight) wire. The pulse makes four trips back and forth along the

cord in 0.8 sec. The tension is the cord will be

- 80 N
- 160 N
- 240 N
- 320 N

**Q.**

A block M hangs vertically at the bottom end of a uniform rope of constant mass per unit length. The top end of the rope is attached to a fixed rigid support at O. A transverse wave pulse (Pulse 1) of wavelength λ0 is produced at point O on the rope. The pulse takes time TOA to reach point A. If the wave pulse of wavelength λ0 is produced at point A (Pulse 2) without disturbing the position of M it takes time TAO to reach point O. Which of the following options is/arc correct?

The time TAO=TOA

The velocities of the two pulses (Pulse 1 and Pulse 2) are same at the midpoint of rope

The wavelength of Pulse 1 becomes longer when it reaches point A.

The velocity of any pulse along the rope is independent of its frequency and wavelength.

**Q.**A wave pulse starts propagating in the x-direction along a non-uniform wire of length 20 m with mass per unit length given by μ=μ0+ax and under a tension of 400 N. Find the time taken by the pulse to travel from the lighter end (x=0) to the heavier end. μ0=10−2 kg/m and a=16×10−3 kg/m2

- 0.4 sec
- 0.8 sec
- 1 sec
- 0.6 sec

**Q.**A ring of mass m and radius R rotates about an axis passing through its centre and perpendicular to its plane with angular velocity ω. Find the velocity of transverse pulse in the ring.

- Rω2
- 2Rω
- Rω
- 32Rω

**Q.**A wave pulse starts propagating in the positive x− direction along a non-uniform wire of length 10 m with a mass per unit length given by m=m0+αx and under a tension of 100 N. Find the time taken by the pulse in seconds to travel from the lighter end x=0 to the heavier end. (m0=10−2 kg/m and α=9×10−3 kg/m2). Answer upto 2 decimal places.

**Q.**On December 2006, a great earthquake occurred off the coast of Sumatra and triggered immense waves (Tsunami) that killed some 200, 000 people. Satellites observing these waves from space measured 800 km from one wave crest to the next and a period between waves of 1 hr. what was the speed of the wave?

400 km/hr

1600 km/hr

800 km/hr

Data insufficient

**Q.**

Equation of travelling wave on a stretched string of linear density $5\raisebox{1ex}{$g$}\!\left/ \!\raisebox{-1ex}{$m$}\right.$ is $y=0.03\mathrm{sin}\left(450t-9x\right)$ where distance and time are measured in $SI$ units. The tension in the string is:

$12.5N$

$7.5N$

$10N$

$5N$

**Q.**Two points on string are being observed as a travelling wave passes them. The points are at x1=0 and x2=l m, the transverse motions of two points are found to be as follows y1=A sin (3 πt) and y2=A sin(3πt+π8) ; t is in seconds and y in metre. Mark correct options

- Frequency of wave is 3 HZ
- Frequency of wave is 1.5 Hz
- Wavelength may be 16 m
- Wavelength may be 1615m

**Q.**Two canoes are 10 m apart on a lake. Each bobs up and down with a period of 4.0 s. When one canoe is at its highest point, the other canoe is at its lowest point. Both canoes are always within a single cycle of the waves. Determine the speed of the wave.

- 4 m/s
- 2.5 m/s
- 5 m/s
- 40 m/s

**Q.**The speed of a transverse wave, travelling on a wire having a length of 100 cm and mass 10 g is 160 m/s. The area of cross-section of the wire is 2 mm2 and its Young's modulus is 32×1011 N/m2. Find the extension of the wire from its natural length.

- 0.08 mm
- 0.04 mm
- 0.02 mm
- 1 mm

**Q.**If the medium changes, for the same wave the frequency remain the same but the speed changes because the wave speed apart of frequency also depends upon:

- All of them
- Amplitude
- Frequency
- Wavelength

**Q.**

An electromagnetic wave of frequency v = 3 MHz passes from vacuum into dielectric medium with permittivity ϵ=4.0 Then

the wavelength is doubled and the frequency remains the same.

the wavelength is doubled and the frequency becomes half.

the wavelength and frequency both remain unchanged.

the wavelength is halved but the frequency remains the same.

**Q.**What is the relation between frequency (ν), wavelength (λ) and speed of the wave (c) ?

- ν=cλ
- ν=2cλ
- ν=cλ
- ν=λc

**Q.**One meter long (both ends open) organ pipe is kept in a gas that has double the density of air at STP. Assuming the speed of sound of air at STP is 300 ms−1, the frequency difference between the fundamental and second harmonic of the pipe is_____Hz.

**Q.**

The downhill movement of masses of rock debris and other materials under the direct influence of gravity is ____

**Q.**Laminar flows takes place between two parallel plates. The distance between the plates is B. The minimum depth of flow from the bottom plate where local velocity is equal to 3/4th the average velocity of flow is kB. The value of k (correct upto two decimal place) is ____.

- 0.14

**Q.**Two independent harmonic oscillators of equal mass are oscillating about the origin with angular frequencies ω1 and ω2 and have total energies E1 and E2, respectively. The variations of their momenta p with positions x are shown in the figures. If ab=n2 and aR=n, then the correct equation(s) is(are):

- E1ω1=E2ω2
- ω2ω1=n2
- ω1ω2=n2
- E1ω1=E2ω2

**Q.**Draw a neat sketch of Ruby Laser. Explain its working with the help of energy level diagram.