Physics Test 4

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Physics Test 4

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Weekly Quiz Competition

Question 1
4 / -1

If the light ray travels in a medium of refractive index √3 and it is incident on the boundary of another medium with refractive index 1.5. Find the minimum angle of incidence such that there is the total internal reflection of the incident ray.

A
30^◦

B
45^◦

C
75^◦

D
60^◦

Solution

Using Snell’s law,

μ₁*sinθ₁= μ₂*sinθ₂

θ₂= 90^◦, μ₁= √3, μ₂= 1.5

Substituting the values,

θ₁= 60^◦
Question 2
4 / -1

If three thin convex lenses with focal lengths 10 cms, 20 cms and 30 cms are placed together. What is the equivalent power of lens system?

A
1.67 D

B
18.33 D

C
5.45 D

D
10.33 D

Solution

Equivalent focal length will be:

1/f= 1/f1 +1/f2 +1/f3 (Where f1= 10 cm, f2= 20 cm, f3= 30 cm)

Substituting the values,

f= 60/11 cm

So power of the lens,

P= 1/f (meter)^-1= 18.33 D
Question 3
4 / -1

Which one of the following is not correct?

A
Huygen’s principle says that light travels in the form of the wave.

B
Wavefront is the surface where the phase of the oscillation is same.

C
The velocity of light remains same when passing from one medium to other.

D
Huygen’s principle states that every point on the wavefront release secondary spherical wavelets of light.

Solution

(A) and (D) are statements of Huygen’s principle and velocity of light do change when it changes medium. Refractive index is the ratio of the velocity of light in the vacuum to the velocity of light in that medium.
Question 4
4 / -1

Which of the following is true?

A
The rate of change of temperature of the body is proportional to the square of its temperature.

B
The rate of change of temperature of the body is proportional to the difference of the body temperature and ambient temperature.

C
The rate of change of temperature of the body is proportional to the fourth power of body temperature.

D
The rate of change of temperature of the body depends only on ambient temperature.

Solution

According to Newton’s law of cooling, Rate of change of body temperature is directly proportional to the difference of body and ambient temperature.
Question 5
4 / -1

Which of the following is the correct statement of the Zeroth law of thermodynamics?

A
Heat flows from the body with higher temperature to lower temperature.

B
The energy of the system is constant throughout.

C
If two bodies are separately in thermal equilibrium with a third body, then they are in thermal equilibrium with each other.

D
Change in entropy of universe can never be negative.

Solution

(B) and (D) are related to the first and the second laws respectively. (A) is the basic principle of thermodynamics. (C) is the correct statement of the Zeroth law of thermodynamics.
Question 6
4 / -1

If 1kg of water at 50^◦C is brought in contact with 200 gm of ice. Find the final temperature of the mixture. (Specific heat of water= 4.18 J/gm/^◦C and Latent heat of ice= 333 J/gm)

A
0^◦C

B
12^◦C

C
34^◦C

D
28^◦C

Solution

To find the final temperature,

Heat absorbed by ice+heat absorbed by water after melting completely = heat released by water

m_ice*L + m_ice*(T-0)*C= m_water*(50-T)*C

Substituting and solving the above equation,

Where L= 333J/gm and C= 4.18 J/gm/◦C

Therefore T= 28.4^◦C
Question 7
4 / -1

For a fixed expansion of volume and for fixed initial pressure, which of the following process has minimum work done during the change?

A
Isothermal process

B
Isobaric process

C
Isentropic process

D
Polytropic process with n<1

Solution

The curve of an Isentropic process is steepest; then isothermal then polytropic process with n<1 and then, Isobaric process. Hence, work done is minimum in Isentropic process.

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Re-Attempt Weekly Quiz Competition

Physics Test 4

Result

Physics Test 4

Score

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Rank

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SHARING IS CARING

Question 1

30◦

45◦

75◦

60◦

Solution

Question 2

1.67 D

18.33 D

5.45 D

10.33 D

Solution

Question 3

Huygen’s principle says that light travels in the form of the wave.

Wavefront is the surface where the phase of the oscillation is same.

The velocity of light remains same when passing from one medium to other.

Huygen’s principle states that every point on the wavefront release secondary spherical wavelets of light.

Solution

Question 4

The rate of change of temperature of the body is proportional to the square of its temperature.

The rate of change of temperature of the body is proportional to the difference of the body temperature and ambient temperature.

The rate of change of temperature of the body is proportional to the fourth power of body temperature.

The rate of change of temperature of the body depends only on ambient temperature.

Solution

Question 5

Heat flows from the body with higher temperature to lower temperature.

The energy of the system is constant throughout.

If two bodies are separately in thermal equilibrium with a third body, then they are in thermal equilibrium with each other.

Change in entropy of universe can never be negative.

Solution

Question 6

0◦C

12◦C

34◦C

28◦C

Solution

Question 7

Isothermal process

Isobaric process

Isentropic process

Polytropic process with n<1

Solution

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30^◦

45^◦

75^◦

60^◦

0^◦C

12^◦C

34^◦C

28^◦C