Hello dear FSC students, I hope you all are doing great. In today’s tutorial, we will have a look at 2nd Year Physics Chapter 19 Solved Questions. I have started a series of tutorials related to the solution of questions given in 2nd-year physics. In the previous tutorial, I have discussed all the questions of chapter18 with the detailed.

In this post, we will have a detailed look at all the questions given in chapter 19 of FSC physics. I will explain all the questions one by one and give an answer to every question in a simple way. So let’s get started with 2nd Year Physics Chapter 19 Exercise Solved Questions

#### 2nd Year Physics Chapter 19 Exercise Solved Questions

• So friends discuss all these questions one by one with the detailed.

#### Question 19.1

• The measurements on which relative motion always agree upon are.
• Speed of light in space.
• The force applying on moving bodies.

#### Question 19.2

• The special theory of relativity says time is not an absolute quantity. It depends on the motion of the frame of reference.
• The information of science relies on observation and calculations. So time passes slowly or dilate.

#### Question 19.3

(a):

• If you are moving in a spaceship with high speed there will be no pulse variation due to the absence of relative motion.

(b):

• As the speed of the spaceship is larger than the earth due to that pulse rate of people in the spaceship will be high as compared to people on the earth.
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#### Question 19.4

• If the speed of light is infinity then we have.

m = m, l = l, t = t , c = ∞.
m= (mo) /(√1 – v2 /∞) = mo / (√1– 0) =mo.
l= lo (√ 1 – v2 /∞) = lo (√ 1 – 0)=lo.
t = to / (√ 1 – v2 /∞)  = to / (√ 1 – 0) =to.
E = m(∞)Square ⇒ ‘E’ is infinity.

#### Question 19.5

• The work done for compression of spring will be transformed into energy.
• As we are familiar with the Einstein energy equation.

E=mc2

• So with the increment in energy mass will also increase.

#### Question 19.6

• The types of emitted radiation from the hot body depend on the temperature of body.
• At less temperature emitted radiation has a larger wavelength. The larger wavelength in the visible region is of RED color so it appears first.

#### Question 19.7

• According to Stepan Boltzmann law energy radiated per second per square meter is given as.

E = σT4

• If the value of temperature is doubled or T’=2T
• Then we have.

E’ = σ(2T)4

E’ = 16σT4

E’=16E

#### Question 19.8

• As we known the formula for the energy of photons is given as.

E=hf=hc/λ since V=fλ

• The energy of photon is.

E=n(hc/λ)

n=Eλ/hc

• The parameters E, h and c are constant so.
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n∝λ

• From this, you can see that photons for red beam are large due to a larger wavelength.

#### Question 19.9

• As we know that.

E=hc/λ

p=h/λ

• As the wavelength of blue light is less due that it has large energy and momentum.

#### Question 19.10

• The formula for energy quanta is given here.

E=hc/λ

• As the wavelength of a radio wave is larger than the X-rays so from above equation it has less energy quanta.