Waves Test

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Waves Test - 14

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Weekly Quiz Competition

Question 1
1 / -0

Mark the correct match.

A
Good reflectors of sound - Tiles, Marble slabs.

B
Bad reflectors of sound - Thick curtains, thick carpets.

C
Good absorbers of sound - Holed cardboard.

D
All

Solution

$$1.$$ Hard objects are good reflection of sound because particles bounce straight off them.
For example - Tiles and Marble slabs.
$$2.$$ Bad reflectors are those objects which absorb sound.
For example - Thick curtains and thick carpets.
$$3.$$ Substances that absorb the sound well are called good absorbers of sound.
For example - Holed cardboard.
Question 2
1 / -0

Mark the correct statement

A
Hard surfaces are good reflectors of sound.

B
Soft surfaces are poor reflector of sound.

C
Bad reflectors of sound are good absorbers of sound.

D
All

Solution

Sound is not reflected equally from different materials. Hard surfaces reflect more sound. Hard surfaces are good reflectors of sound.
Soft or porous surfaces are poor reflectors of sound.
Bad reflectors of sound are good absorbers of sound. These sound absorbing materials are used to corner walls, ceiling etc.
Question 3
1 / -0

The quantity $$\dfrac{1}{\lambda}$$ is known as:

A
wave velocity

B
frequency

C
wavelength

D
wave number

Solution

The quantity $$\frac{1}{\lambda}$$ is known as wave number. It is the spacial frequency of a wave, measured in cycles per unit distance or radians per unit distance.
Question 4
1 / -0

When a wave travels in a medium, _______ is transferred from one place to other with the wave.

A
mass

B
velocity

C
density

D
energy

Solution

Energy is transferred from one place to another when a wave travels in a medium.
Question 5
1 / -0

Soundproof walls use materials that

A
absorbs sound

B
reflects sound in all directions

C
reflects sound in only one direction

D
amplify sound waves on one side and weaken sound waves on other

Solution

Soundproof materials absorb most of the sound waves incident on it and minimize echoes.
Question 6
1 / -0

Sound waves get reflected from :

A
plane surfaces

B
spherical surfaces

C
hard surfaces

D
all of these

Solution

Sound waves, like light waves, also get reflected from hard surfaces both plane and spherical in shape.
Question 7
1 / -0

Mark the correct statements.
(I) directions in which the sound is incident and is reflected make equal angles with the normal to the reflecting surface.
(II) reflection of sound occurs from a polished surface.
(III) reflection of sound occurs from rough surface.

A
I, II

B
I, III

C
II, III

D
I, II, III

Solution

Sound bounces off a solid or a liquid like a rubber ball bounces off a wall. Like light, sound gets reflected at the surface of a solid or liquid and follows the same laws of reflection as you have studied in earlier classes. The directions in which the sound is incident and is reflected make equal angles with the normal to the reflecting surface, and the three are in the same plane. An obstacle of large size which may be polished or rough is needed for the reflection of sound waves.
Question 8
1 / -0

Two particles on a wave having wavelength $$2$$m are at the distances of $$5$$m and $$9$$m respectively from origin. The phase difference between the particles is ________.

A
$$\displaystyle\frac{\pi}{2}$$ rad

B
$$\pi$$ rad

C
$$2\pi$$ rad

D
$$4\pi$$ rad

Solution

Distance between the particles is $$4m$$.
$$\Delta \varphi =\dfrac { d }{ \lambda } \times 2\pi =\dfrac { 4 }{ 2 } \times 2\pi =4\pi $$
Question 9
1 / -0

Working of radars in oceans is based on the principle of

A
geo-positional system

B
reflection of sound

C
locus of sound waves

D
none

Solution

Radars in oceans employ sound waves to detect the location of surrounding objects.
Question 10
1 / -0

The frequency of light in air is $$5\times 10^{14}Hz$$. What will be the frequency of light, when it enters in the water?

A
$$2.5\times 10^{14}Hz$$

B
$$5\times 10^{14}Hz$$

C
$$10^{15}Hz$$

D
$$2.5\times 10^{12}Hz$$

Solution

In refraction only velocity of light and the wavelength of light change
When light enters from air or vacuum, ie, when light goes from one medium to other, then its frequency does not change ie, remains unchanged.
Hence frequency of light will remain $$5\times 10^{14}Hz$$.

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Re-Attempt Weekly Quiz Competition

Waves Test - 14

Result

Waves Test - 14

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Rank

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SHARING IS CARING

Question 1

Good reflectors of sound - Tiles, Marble slabs.

Bad reflectors of sound - Thick curtains, thick carpets.

Good absorbers of sound - Holed cardboard.

All

Solution

Question 2

Hard surfaces are good reflectors of sound.

Soft surfaces are poor reflector of sound.

Bad reflectors of sound are good absorbers of sound.

All

Solution

Question 3

wave velocity

frequency

wavelength

wave number

Solution

Question 4

mass

velocity

density

energy

Solution

Question 5

absorbs sound

reflects sound in all directions

reflects sound in only one direction

amplify sound waves on one side and weaken sound waves on other

Solution

Question 6

plane surfaces

spherical surfaces

hard surfaces

all of these

Solution

Question 7

I, II

I, III

II, III

I, II, III

Solution

Question 8

$$\displaystyle\frac{\pi}{2}$$ rad

$$\pi$$ rad

$$2\pi$$ rad

$$4\pi$$ rad

Solution

Question 9

geo-positional system

reflection of sound

locus of sound waves

none

Solution

Question 10

$$2.5\times 10^{14}Hz$$

$$5\times 10^{14}Hz$$

$$10^{15}Hz$$

$$2.5\times 10^{12}Hz$$

Solution

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