Practice MCQ Questions and answers on Physics-GK

21

An optically plane surface reflects a beam of light

A) As a parallel beam in one direction B) As diffused beams in all directions C) As parallel beams in all directions D) As a diffused beam in one direction

Discuss

Answer & Solution

Answer: Option A

Solution:

An optically plane surface reflects a beam of light as a parallel beam in one direction. The set of incident rays are reflected as a set of rays. This type of reflection of a set of rays is called Specular Reflection.

22

The focal length of a concave mirror with a radius of curvature of 20.0 cm is :

A) 20 cm B) 5 cm C) 10 cm D) 15 cm

Discuss

Answer & Solution

Answer: Option C

Solution:

Let us assume f is focal length
R is radius of curvature
According to the formula R = 2f
f = R/2
= 20/2
= 10 cm

23

The type of mirrors used in the headlamp of cars is

A) Parabolic concave B) Plane C) Spherical convex D) Cylindrical concave

Discuss

Answer & Solution

Answer: Option A

Solution:

A concave mirror is used in the headlight of a car. The reason being that a concave mirror is a converging mirror as opposed to a convex mirror which is a diverging mirror. In headlights the bulb is kept at the focus of the mirror.

24

Shaving mirror is

A) Convex B) Concave C) Plane D) Parabolic

Discuss

Answer & Solution

Answer: Option B

Solution:

A shaving mirror gives an enlarged image. The mirror is concave. You must have your face within the focal length of the mirror, to get an upright and enlarged image.

25

What changes will happen to a bowl of ice and water kept at exactly zero degree Celsius ?

A) All ice will melt B) All water will become ice C) No change will happen D) Only some ice will melt

Discuss

Answer & Solution

Answer: Option C

Solution:

Fresh water cooled to zero degree Celsius and subjected to additional loss of heat energy normally will freeze. A mixture of fresh water and ice has an equilibrium temperature of zero degree Celsius. Adding heat to the mixture causes ice to melt whereas removing heat causes water to freeze. So, no change will happen.

26

At what temperature do the Fahrenheit and Celsius scales give the same reading?

A) 212 degrees B) 32 degreees C) -40 degreees D) 0 degreees

Discuss

Answer & Solution

Answer: Option C

Solution:

The temperature when both the Celsius and Fahrenheit scales are the same is -40 degrees.

27

The temperature of a liquid is 32° F. What is its temperature in Celsius scale?

A) 32° C B) 0° C C) 100° C D) 212° C

Discuss

Answer & Solution

Answer: Option B

Solution:

The Fahrenheit scale defines the freezing point of water as 32°F and the boiling point as 212°F. The Celsius scale sets the freezing point and boiling point of water at 0°C and 100°C respectively.

28

To convert temperature from Celcius to Kelvin scale, you must ________ the given temperature.

A) Subtract 273 B) Multiply 273 C) Add 273 D) Divide by 273

Discuss

Answer & Solution

Answer: Option C

Solution:

Take your Celsius temperature and add 273. Your answer will be in Kelvin.

29

0°K is equivalent to

A) 273°C B) – 273°C C) 0°C D) 100°C

Discuss

Answer & Solution

Answer: Option B

Solution:

0°K is equivalent to – 273°C.

30

In very cold countries alcohol is used as a thermometric liquid because

A) Alcohol is a poor conductor of heat B) Alcohol can be coloured for its level to be seen easily C) Its freezing point is very low D) It will not stick to the glass tube

Discuss

Answer & Solution

Answer: Option C

Solution:

Alcohol has a freezing point as low as -117^oC. So it won't freeze even in very cold countries.