Doppler Effect in Light Waves

Q. the speed of sound in hydrogen at NTP, is 1270 m/s. then speed in a mixure of hydrogen and oxygen in the ratio 4:1 by volume (in m/s) will be (1) 635 (2) 318 (3) 158 (4) 1270

Q. 7.In space of horizontal electric field (E = mg/q ) exist as shown in figure and a mass m attached at the end of a light rod. If mass m is released from the position shown in figure. Find the angular velocity of the rod when it passes through the bottom most point

Q.

A person feels 2.5% difference of frequency of a motor-car horn. If the motor-car is moving to the person and the velocity of sound is 320 m/sec, then the velocity of car will be

1. 7 m/s

2. 6 m/s (approx.)

3. 8 m/s (approx.)

4. 5 m/s

Q. A light rod carries three equal masses A, B and Cas shown in the figure. What will be the velocity ofB in the vertical position of the rod, if it is releasedfrom horizontal position as shown in the figure?

Q. 69.Assuming sun to have spherical outer surface of radius r, radiating like a black body at temperature t^0C, the power received by a unit surface at a unit distance R normal to the Rays from the centre of the sun is ?

Q.

A source of sound of frequency 450 cycles/sec is moving towards a stationary observer with 34 m/sec speed. If the speed of sound is 340 m/sec, then the apparent frequency will be

1. 410 cycles/sec

2. 500 cycles/sec

3. 550 cycles/sec

4. 450 cycles/sec

Q. The speed of sound in oxygen (O2)at a certain temperature s460 ms1. The speed of sound in helium (He) at the samsetemperature will be (assume both gases to be ideal)AIEEE 2008(a) 500 ms-1(c) 330 ms"1A wavelength 0.60 cm is produced in air and it travels at a(b) 650 ms(d) 1420 msd f 300 ms1. It will be anUPSEAT 2000

Q. A train, standing in a station-yard, blows a whistle of frequency 400 Hz in still air. The wind starts blowing in the direction from the yard to the station with a speed of 10 m s¯¹. What are the frequency, wavelength, and speed of sound for an observer standing on the station’s platform? Is the situation exactly identical to the case when the air is still and the observer runs towards the yard at a speed of 10 m s¯¹? The speed of sound in still air can be taken as 340 m s¯¹

Q. THE WAVELENGTH OF SOUND WAVES IN HYDROGEN GAS CORRRSPONDING TO THE LOWER LIMIT OF AUDIBILITY I

Q. An observer is moving with half the speed of light towards a stationary microwave source emitting waves at frequency $10\text{GHz}$. What is the frequency in GHz of the microwave measured by the observer?
(speed of light $=3\times {10}^8{\text{ms}}^{-1}$). Answer the nearest integer.

Q.

A bullet of mass 5 g moving at a speed of 200 m/s strikes a rigidly fixed wooden plank of thickness 0.2 m normally and passes through it losing half of its kinetic energy. If it again strikes an identical rigidly fixed wooden plank and passes through it, assuming the same resistance in the two planks, the ration of the thermal energies produced in the two planks is

1. 1:1

2. 2:1

3. 4:1

4. 1:2

Q. At the first minimum of a single-slit diffraction pattern, the phase difference between the Huygens wavelet, from the edge of the slit and the wavelet from the mid-point of the slit is,

1. $\pi \text{rad}$
2. $\frac{\pi }{4}\text{rad}$
3. $\frac{\pi }{2}\text{rad}$
4. $\frac{\pi }{8}\text{rad}$

Q.

As the intensity of incident light increases

1. Photoelectric current increases

2. Photoelectric current decreases

3. Kinetic energy of emitted photoelectrons increases

4. Kinetic energy of emitted photoelectrons decreases

Q. 84.How a areploane flu in the sky and it is turning out