Reflection from an Open End

Q.

The equation of a wave travelling on a string stretched along the X-axis is given by

$y=A{e}^{-(\frac{x}{a}+\frac{t}{T}{)}^2}$.

(a) Write the dimensions of a and T. (b) Find the wave speed. (c) In which direction is the wave travelling ? (d) Where is the maximum of the pulse located at t = T ? At t = 2T ?

Q. For photoelectric emission from a certain metal the cut off frequency is v. If radiation of frequency 2v impinges on the metal plate, the maximum possible velocity of the emitted electron will be (m is the electron mass).

1. $\sqrt{\frac{hv}{\left(2m\right)}}$
2. $\sqrt{\frac{hv}{m}}$
3. $\sqrt{\frac{2hv}{m}}$
4. $2\sqrt{\frac{hv}{m}}$

Q.

What are the applications of sound?

Q. Two waves travelling in opposite directions produce a standing wave. The individual wave functions are given by $y_1=4\sin (3x-2t)\text{cm}$ and $y_2=4\sin (3x+2t)\text{cm}$, where $x$ and $y$ are in $\text{cm}$ then :
(Use $\sin \left(6.9\right)=0.57$ if required.)

1. The maximum displacement of the motion at $x=2.3\text{cm}$ is $4.63\text{cm}$
2. The maximum displacement of the motion at $x=2.3\text{cm}$ is $5.32\text{cm}$
3. Nodes are formed at $x$ values given by $0,\frac{\pi }{3},\frac{2\pi }{3},\pi ,\frac{4\pi }{3},\dots$
4. Antinodes are formed at $x$ values given by $\frac{\pi }{6},\frac{\pi }{2},\frac{5\pi }{6},\frac{7\pi }{6},\dots$

Q. A wave pulse is generated in a string that lies along $x-$ axis. At the points $A$ and $B$, as shown in figure, if $R_A$ and $R_B$ are ratio of wave speed to the particle speed respectively, then

1. $R_A=R_B$
2. $R_A>R_B$
3. $R_B>R_A$
4. Information insufficient

Q.

A wave pulse passing on a string with a speed of $40cm{s}^{-1}$ in the negative x-direction has its maximum at x = 0 at t = 0. Where will this maximum be located at t = 5 s ?

Q. A sound source is moving towards a stationary observer with $\frac{1}{10}$ of the speed of sound. The ratio of apparent to real frequency is

1. 10/9
2. 11/10
3. (11 / 10)²
4. (9 / 10)²

Q. What happens when a sound wave is reflected from the boundary of a denser medium? The compression of the incident wave is returned as a

1. Rarefaction
2. Sound wave disappears.
3. Compression
4. Both (a) and (b)

Q.

What are analog signals?

Q. Emw of intensity I falling normally on a perfectly reflecting surface. The pressure exerted by wave on the surface is

Q. The thickness of a half-wave plate for an electromagnetic wave of wavelength 9000A will be (refractive index for the ordinary light is 1.5533 and refractive index for extraordinary light u =1.5443 ) Options: 50 micron 25 micron 75 micron 100 micron

Q. A car moving towards a wall at velocity of $10m/s$ blows a horn of frequency $100Hz$. Frequency of horn sound that is reflected from wall is [velocity of sound is $340m/s$]

1. $97Hz$
2. $105Hz$
3. $98Hz$
4. $103Hz$

Q.

A cylindrical metal tube has a length of 50 cm and is , open at both ends. Find the frequencies between 1000 Hz and 2000 Hz at which the air column in the tube can resonate. Speed of sound in air is $340m{s}^{-1}$.

Q.

A string of linear mass density $0.5gc{m}^{-1}$ and a total length $30cm$ is tied to a fixed wall at one end and to a frictionless ring at the other end. The ring can move on a vertical rod. A wave pulse is produced on the string which moves towards the ring at a speed of $20cm{s}^{-1}$. The pulse is symmetric about its maximum which is located at a distance of $20cm$ from the end joined to the ring. Assuming that the wave is reflected from the ends without loss of energy, find the time taken by the string to regain its shape.

1. None of these

2. 2 sec

3. 1sec

4. 4 sec

Q.

Power dissipation is maximum

1. At peak

2. At resonance

3. At

4. At

Q. Velocity of sound in air is $332m{s}^{-1}$. Its velocity in vacuum will be

1. $>332m{s}^{-1}$

2. $=332m{s}^{-1}$
3. $<332m{s}^{-1}$
4. None of these

Q.

A string of linear mass density $0.5gc{m}^{-1}$ and a total length 30 cm is tied to a fixed wall at one end and to a frictionless ring at the other end (figure 15-E4). The nng can move on a vertical rod. A wave pulse is produced, on the string which moves towards the ring at a speed of $20cm{s}^{-1}$. The pulse is symmetric about its maximum, which is located at a distance of 20 cm from the end joined to the ring. (a) Assuming that the wave is reflected from the ends without loss of energy, find the time taken by the string to regain its shape. (b) The shape of the string changes periodically with time.Find this time period. (c) What is the tension in the string ?

Q. Change in temperature of medium changes the

1. frequency of sound wave
2. amplitude of sound wave
3. waveform of sound wave
4. wavelength of sound wave

Q.

In class, while teaching Huygens principle we were taught that a tertiary wavelet exist inner to the original wavefront. But while reading the text I got a notion that backwave doesn't exist. So does it really exist? If not, why doesn't it exist?

Q.

Three resonant frequencies of a string are 90, 150 an 210 Hz. (a) Find the highest possible funclamera frequency of vibration of this string. (b) Which harmonics of the fundamental are the given frequencies ? (c) Which overtones are these frequencies ? (d) If the length of the string is 80 cm, what would be the speed of a transverse wave on this string?

Q. A source of sound waves is travelling as shown. In which situation would the stationary observer detect the largest decrease in the observed frequency?

[Assume, medium is stationary]

1. 
2. 
3. 
4. 

Q.

What is meant by coherence?

Q.

What are the two types of coherence?

Q. Which of the following statements are true for wave motion? (a) Mechanical transverse waves can propagate through all mediums. (b) Longitudinal waves can propagate through solids only. (c) Mechanical transverse waves can propagate through solids only. (d) Longitudinal waves can propagate through vacuum.

Q. What is the meaning of vibration of electric field vector in electromagnetic waves?

Q. ifincidenr ray is 40degree with respect to normal then what would be the angle between reflected ray and incident ray

Q. Statement-1 : When a longitudinal pressure wave is reflected at the open end of an organ pipe, the compression pressure wave pulse becomes rarefraction pressure wave pulse during the reflection.
Statement-2 : The phase of the wave changes by when reflected at the open end.

1. Both the statements are true but statement-2 is not the correct explanation of statement-1
2. Statement-1 is true and statement-2 is false
3. Both the statements are true and statement-2 is the correct explanation of statement-1
4. Statement-1 is false and statement-2 is true

Q. An organ pipe, open at both ends, contains
(a) longitudinal stationary waves
(b) longitudinal travelling waves
(c) transverse stationary waves
(d) transverse travelling waves.

Q. Two organ pipes of lengths 40 cm and 40.4 cm oscillate together. The pair produces sound of variable intensity and between two consecutive maximas, we get 0.25 s. Then the speed of sound in air is about

1. 330 m/s
2. 342 m/s
3. 324 m/s
4. 360 m/s

Q. While comparing the LC oscillations with the oscillations of a spring-block system, with which parameter of the spring-block system, the current in the LC circuit can be compared?

1. Displacement
2. Velocity
3. Acceleration
4. None of these