Wavelength

Q.

A hospital uses an ultrasonic scanner to locate tumours in a tissue. What is the wavelength of sound in the tissue in which the speed of sound is $1.7km{s}^{-1}$? The operating frequency of the scanner is 4.2 MHz.

Q.

To observed diffraction, The size of the obstacle

1. Should be much larger than the wavelength

2. has no relation to wavelength

3. should be of the order of wavelength.

4. should be $\frac{\lambda }{2}$ , where $\lambda$ is the wavelength

Q. Transverse waves are generated in two uniform wires $A$ and $B$ of the same material by attaching their free ends to a vibrating source of frequency $200\text{Hz}$. The cross-sectional area of $A$ is half that of $B$ while the tension on $A$ is twice that on $B$. The ratio of the wavelengths of the transverse waves in $A$ and $B$ is

1. $1:\sqrt{2}$
2. $\sqrt{2}:1$
3. $1:2$
4. $2:1$

Q. When photons of energy $hv$ fall on an aluminium plate (work function $E_0)$, photoelectrons of maximum kinetic energy $K$ are ejected. If the frequency of radiation is doubled, the maximum kinetic energy of the ejected photoelectrons will be

1. $K+hv$
2. $K+E_0$
3. $2K$
4. $K$

Q.

Why Is It necessary to use coherent sources to make light interfere?

Q. Suppose that the electric field part of an electromagnetic wave in vacuum is E = {(3.1 N/C) cos [(1.8 rad/m) y + (5.4 × 106 rad/s)t]}ˆi . (a) What is the direction of propagation? (b) What is the wavelength l ? (c) What is the frequency n ? (d) What is the amplitude of the magnetic field part of the wave? (e) Write an expression for the magnetic field part of the wave.

Q.

To demonstrate the phenomenon of interference we require two sources, which emit radiations of

1. Two sources that emit radiation of the same frequency

2. Two sources that emit radiation of nearly the same frequency

3. Two sources that emit radiation of the same frequency and have a definite phase relationship

4. Two sources that emit radiation of different wavelengths

Q.

A heavy but uniform rope of length L is suspended from a ceiling. (a) Write the velocity of a transverse wave travelling on the string as a function of the distance from the lower end. (b). If the rope is given a sudden sideways jerk at the bottom, how long will it take for the pulse to reach the celiling ? (c) A particle is dropped from the ceiling at the instant the bottom end is given the jerk. Where will the particle meet the pulse ?

Q.

If the two wavelength of 800 NM and 600NM are used to get interference on screen 1.4 m away the distance of the two slit is 0.3 mm find the least distance from centre of fringe where the bright fringe of two will coincide

Q.

Stationary waves of frequency $200Hz$ are formed in the air. If the velocity of the wave is $360m/s$, the shortest distance between two antinodes is

1. $1.8m$

2. $3.6m$

3. $0.9m$

4. $0.45m$

Q. The waves of 600 μ m wavelength are incident normally on a slit of 1.2 mm width. the value of diffraction angle corresponding to the first minima will be (in radian

Q. Which mode of propagation is used by short wave broadcast services ?

Q. 2.13.Find the frequency of 1 MeV photon. Given wavelength of a 1keV photon is 1.24 x 10m

Q.

Light of wavelength 500 nm is incident on a slit of width 0.1 mm. The width of the central bright line on the screen is 2m. What is the distance of the screen?

1. 0.75 m

2. 1 m

3. 2 m

4. 0.5 m

Q. A wave travels on a light string. The equation of the wave is y = A sin $(kx–\omega t+{30}^{\circ })$. It is reflected from a heavy string tied to an end of light string at x = 0. If $36\%$ of the incident energy is reflected, then the equation of the reflected wave is:

1. $y=0.6Asin(kx+\omega t+{30}^{\circ })$
2. $y=0.6Asin(kx+\omega t-{30}^{\circ })$
3. $y=0.6Asin(kx-\omega t+{30}^{\circ }+{180}^{\circ })$
4. $y=0.6Asin(kx+\omega t+{30}^{\circ }+{180}^{\circ })$

Q.

Do coherent sources have same wavelength

Q. A water surfer is moving at a speed of 15 m/s. When he is surfing in the direction of wave, he swingsupwards every 0.8 s because of wave crests. While surfing in opposite direction to that of wave motion, he swings upwards every 0.6 s. Determine the wavelength of transverse component of the water wave.

1. Information insufficient
2. 21.6 m
3. 10.3 m
4. 15 m

Q. A longitudinal wave is produced on a slinky toy. The wave travels at a speed of $30\text{cm/s}$ and the frequency of the wave is $20\text{Hz}$. What is the minimum separation between two consecutive compressions of the slinky toy ?

1. $2.5\text{cm}$
2. $1.5\text{cm}$
3. $0.5\text{cm}$
4. $1.8\text{cm}$

Q.

What waves are used in telecommunication devices?

Q. A single slit of width $a$ is illuminated by violet light of wavelength $4000\dot{A}$ and the width of the central maximum is measured as $y$. When half of the slit width is covered and illuminated by yellow light of wavelength $6000\dot{A}$, the width of the central maxima is

1. $\frac{3y}{2}$
2. $\frac{y}{3}$
3. $3y$
4. $y$

Q. Consider two coherent monochromatic sources $S_1$ and $S_2$, each of wavelength $\lambda$ and separated by a distance $d$. The ratio of the intensity of $S_1$ and $S_2$ is $4$. A detector moves on the line perpendicular to $S_1{S}_2$ as shown in the figure. If the resultant intensity at point $P$ is equal to $\frac{9}{4}$ times intensity of $S_1$, then the distance of $P$ from $S_1$ is,
(Given : $d>0$ and $n$ is a positive integer)

1. $\frac{d^2-n^2{\lambda }^2}{2n\lambda }$
   
2. $\frac{d^2+n^2{\lambda }^2}{2n\lambda }$
   
3. $\frac{n\lambda d}{\sqrt{d^2-n^2{\lambda }^2}}$
   
4. $\frac{2n\lambda d}{\sqrt{d^2-n^2{\lambda }^2}}$
   

Q. Two coherent narrow slits emitting light of wavelength $\lambda$ in the same phase are placed parallel to each other at a small separation of $2\lambda$. The light is collected on a screen $S$ which is placed at a distance $D(>>\lambda )$ from the slit $S_1$ as shown in figure. Find the finite distance $x$ such that the intensity at $P$ is equal to the intensity at $O$.

1. $x=\sqrt{2}D$
2. $x=\sqrt{3}\lambda$
3. $x=\sqrt{3}D$
4. $x=\lambda$

Q.

Indicate the interval which represents one full wavelength.

1. $A$ to $C$

2. $B$ to $D$

3. $A$ to $G$

4. $C$ to $G$

Q. all about resolution and wavelength relationship

Q. What physical quantity is the same for X-rays of wavelength10–10 m, red light of wavelength 6800 Å and radiowaves of wavelength 500m?

Q. For Balmar series, wavelength of first line is λ1 and for Brackett series, wavelength of first line is λ2, then λ1/λ2 is?

Q.

If an antenna radiates electromagnetic waves from a height h, then the range d upto which the signal can be detected is given by ( R is the radius of the earth)

1. 

2. 

3. 

4. 

Q. A plane electromagnetic wave travels in vacuum along z -direction.What can you say about the directions of its electric and magnetic field vectors? If the frequency of the wave is $30\text{MHz}$, what is its wavelength?

Q. We do not choose to transmit and audio signal by Just Directly converting it to an em wave of the same frequency. give two reasons for the same

Q.

What is meant by Coherent Sources?