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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 sound is heard. But in box B there are air... 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 bubble shines in water is... 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.... View Article

How is sound produced?

Sound is produced by vibrating bodies.... View Article

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 between these surfaces.... 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 the... 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 meet but appear to meet when they are... 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 the right. If you apply the... 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 believed something like this for centuries, till... 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 CWe know that, q = neSo no. of electrons, n = q/e = 600 / (1.6x10-19) = 375x1019... 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. When the image formation... 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... View Article

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 cases rubbing of glass would... 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 without slipping easily due to the normal... View Article

If a ray of light is incident at an angle of 60 degrees to the normal, then the angle formed by the reflected ray with the normal is equal to

According to the first law of reflection, the angle of incidence is equal to the angle of reflection ... View Article

A 1 cm high object is placed at a distance of 32 cm from a concave mirror. The image is real, inverted and 1.5 cm in size. Calculate the focal length of the mirror and the position of the image.

Given that Distance of the object placed from a concave mirror u = -32 cm ho = 1cm As the image is inverted, the magnification must be... View Article

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