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Multiple choice physics sound time period, frequency and amplitude of sound amplitude, time period and frequency of a vibration nature and characteristics of sound waves

The sound produced by an object vibrating with a high frequency is called _____________ .

  1. shrill or high-pitched sound

  2. deep or low-pitched sound

  3. heavy sound

  4. musical sound
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The frequency determines the shrillness or pitch of a sound. If the frequency of vibration is higher, we say that the sound is shrill and has a higher pitch. If the frequency of vibration is lower, then we say that the sound has low pitch.

Multiple choice physics sound time period, frequency and amplitude of sound amplitude, time period and frequency of a vibration nature and characteristics of sound waves

State whether true or false :

Shrill sound is a high-pitch sound and a soft sound is a low-pitch sound.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The vocal cords of women are thicker than men , therefore they produce a shrill sound , which we know has higher frequency or higher pitch , whereas men's voice is grave , means low frequency i.e. lower pitch .

Multiple choice physics effects of light scattering of light and its applications some natural phenomena of light natural phenomena explained by scattering

Which of the following statement is correct?

  1. At sunset or sunrise, the suns rays have to pass through a small distance in the atmosphere.

  2. At sunset or sunrise the suns rays have to pass through a larger distance in the atmosphere.
  3. Rayleigh scattering which is proportional to $(l/\lambda)^2$

  4. Most of the blue and other shorter wavelengths are not removed by scattering.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

At sunset or sunrise the suns rays have to pass through a larger distance in the atmosphere and most of the blue and other shorter wavelengths are remove by scattering.

Multiple choice physics effects of light scattering of light and its applications some natural phenomena of light natural phenomena explained by scattering

An astronaut in a spaceship the sky appears black due to:

  1. Absence of atmosphere in his neighbourhood

  2. Light from the sky is absorbed by the medium surrounding him

  3. The fact at the height, sky radiations are only in the infra-red and the ultraviolet region

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

To an astronaut it will appear as black.On earth we see the blue sky due to presence of atmosphere. Atmosphere refracts light ray coming from the sun and we see the colour of sky.In space, due to the absence of the atmosphere the light rays do not refract and reach the astronomer's eyes therefore it appears black.

Multiple choice physics effects of light scattering of light and its applications some natural phenomena of light natural phenomena explained by scattering

One cannot see through fog because .......... .

  1. Fog absorbs light

  2. Refractive index of fog is unity

  3. Light suffers total internal reflection at the droplets in fog

  4. Light is scattered by the droplets in fog
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Answer is D.
We cannot see through fog because of scattering.
Atoms and molecules in the air, including anything carried in the air like dust or smoke, will scatter light. Water droplets, as they are present in fog, also scatter light. The light falling on an object and reflected to a viewer can be scattered to heck and back before it gets to the place where it can be 'seen' by an observer. So the observer just sees a 'whiteout' instead of being able to make out anything beyond a few meters or so.

Multiple choice physics effects of light scattering of light and its applications some natural phenomena of light natural phenomena explained by scattering

Planets do not twinkle as stars, because :

  1. Planets are much closer to earth than stars

  2. Planets are smaller in size than stars

  3. A planet is not surrounded by gaseous atmosphere

  4. A star is not surrounded by gaseous atmosphere
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer is A.

Stars, except for the Sun, although they may be millions of miles in diameter, are very far away.  They appear as point sources even when viewed by telescopes.  The planets in our solar system, much smaller than stars, are closer and can be resolved as disks with a little bit of magnification. 
Since the Earth's atmosphere is turbulent, all images viewed up through it tend to 'swim.' The result of this is that sometimes a single point in object space gets mapped to two or more points in image space, and also sometimes a single point in object space does not get mapped into any point in image space.  When a star's single point in object space fails to map to at least one point in image space, the star seems to disappear temporarly.  This does not mean the star's light is lost for that moment.  It just means that it didn't get to your eye, it went somewhere else.
Since planets represent several points in object space, it is highly likely that one or more points in the planet's object space get mapped to a points in image space, and the planet's image never winks out.  Each individual ray is twinkling away as badly as any star, but when all of those individual rays are viewed together, the next effect is averaged out to something considerably steadier.
The result is that stars tend to twinkle, and planets do not.