When we crack a whip, a loud noise is created. Why?
When we crack a whip, speed of the tip is greater than that of sound. If the speed of a... View Article
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Dispersive power depends upon
Dispersive power depends upon the nature of the material. What is dispersive power? Dispersive power of prism is defined as... View Article
Which of the following correctly represents the increasing order of frequency for infrasound, ultrasound and audible range?
Infrasound – Less than 20Hz Audible Range – 20Hz to 20KHz Ultrasound – Greater than 20Khz
A converging lens is used to form an image on a screen. When upper half of the lens is covered by an opaque screen [IIT-JEE 1986; SCRA 1994; MP PET 1996; MP PMT 2004; BHU 1998, 05]
a) Half of the image will disappear b) No part of the image will disappear c) The intensity of the... View Article
Which of the following correctly represents the increasing order of frequency ?
Infrasound – Less than 20Hz,Audible Range – 20Hz to 20KHz, Ultrasound – Greater than 20Khz
Choose the correct option Statement 1: Sound cannot travel in vacuum. Statement 2 :Sound is a mechanical wave and propagates as an oscillation of particles through the medium. So they cannot travel in vacuum.
Sound waves propagate through to and fro motion of particles of the medium. Since there are no particles in vacuum,... View Article
There are two boxes A & B. Cell phones are kept in both the boxes, all air is sucked from box A and then closed by a device. While box B is simply closed by a device without sucking air from it. A call is made simultaneously on both the phones, but sound comes only from box B. This is because Statement 1 : In box B there are air particles to vibrate but in box A there is vacuum Statement 2 : Sound needs a medium for propagation
In box A, there are no air particles to vibrate, so sound does not propagates in box A and no... View Article
What is the reason for shiny air bubble in the water?
A) Dispersion B) Refraction C) Diffraction D) Total internal reflection The right option is D. The reason why the air... View Article
Statement 1 : Sound needs a medium for its propagation Statement 2 : Sound does not propagate in vacuum , as it does not have particles to vibrate.
Since sound is produced by vibration .In vacuum there are no particles to vibrate so, no sound is produced.
How is sound produced?
Sound is produced by vibrating bodies.
When a lubricant is applied between two surfaces, the movement becomes smooth as the interlocking of irregularities is avoided to a great extent.
Friction is caused due to interlocking of irregularities in the surfaces. When a lubricant is applied, it forms a layer... View Article
would be the impact on friction if powder is sprinkled on the carom board?
Sprinkling of powder makes the surface of the board smoother than before due to comparatively less inter-locking between irregularities of... View Article
Can a virtual image be formed on a screen?
Virtual images cannot be obtained on the screen because the image formed is from the light rays that do not... View Article
In which of the following directions does the force of friction act
The force of friction always opposes the applied force. If you apply the force along the left, friction acts along... View Article
You can ‘see’ with the help of:
C. If the answer was A, how come we can’t see anything in the dark It is funny that people... View Article
A TV set shoots out a beam of electrons. The beam current is 10 A. How many electrons strike the TV screen in a minute?
Total charge, q = It = 10 A x 60 s = 600 C We know that, q = ne... View Article
Myopia is also known as?
Myopia is also known as near-sightedness. Myopia is one of the most common impaired vision found in people under 40.... View Article
For how long time period should a flow of 10^19 electrons be maintained between two points A and B to have a constant current of 8 A between them?
We know that, q=ne Also, I = q/t Hence, t = ne/I = (1019 x 1.6 x10-19) / 8 = 0.2 s
In which of the following cases minimum heat will be released?
In the above cases, rubbing of glass would have less resistive force due to poor interlocking. So, among the given... View Article
For surfaces pertaining to grass and dirt, shoes with spikes are used by the athletes. What impact do spikes have?
Spikes on the soles of shoes increase the grip as the spikes allows the runner to push off the ground... View Article
