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 20 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 chapter20 with the detailed.

In this post, we will have a detailed look at all the questions given in chapter 21 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 21 Exercise Solved Questions.

#### 2nd Year Physics Chapter 21 Exercise Solved Questions

• So friends let’s discuss all questions one by one with the detail.

#### Question 21.1

• The nuclei of similar elements that have a different mass number and same charge number are called isotopes of an element.

• The atomic number of isotopes is similar.
• Their chemical properties are similar.
• They also have the same number of protons.
• Their number of neutrons is different.
• Their physical properties are different.
• Their mass number is different.

#### Question 21.2

• Less weight and stable nuclei have the same number of protons and neutrons.
• While heavyweight nuclei like 238U92 Uranium consists of 92 protons and 146 neutrons.
• The 226Ra88 Radium consists of eighty-eight protons and 138 neutrons. Due to a large difference among the number of protons and neutrons heavyweight nuclei are unstable.
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#### Question 21.3

• If the half-life of any element is one year then after passing a one year there will be half atoms will remain behind un decay.
• After further one year, half of un decay atoms will leaving behind 1/4 of atoms un-decay.
• From this, you can see that after 2 years element is not completely vanished but only 3/4 of total atoms decayed.

#### Question 21.4

• Suppose that at the start there are ‘N’ numbers of radioactive atoms exits. After one 1/2 life, half atoms will decay, after the second year, N/4 atoms will decay.
• After 2 years decayed atoms will be (N/2 + N/4) = 3/4th of the radioactive element.

#### Question 21.5

• The half-life of 226Ra88 is 1.6 * 103 so after 1.6 * 103 1/2 of 226Ra88 will decay.
• After another half-life half atoms will decay so there is infinity time is required to complete decay of an atom.
• Due to this reason still, we have 226Ra88 atoms un-decay.

#### Question 21.6

• There are three techniques through which electromagnetic rays interact with the matter. These techniques are given here.
• Photoelectric Effect
• Pair production
• Compton Effect
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#### Question 21.

• As we know the charge on alpha particle is plus 2 and beta particle is a negative charge.
• Due to charges, these 2 particles have the ability to ionize the atoms without colliding the electrons.
• When the alpha particle comes close to an atom it gets electron and ionized the atom.
• When beta particle comes close to an atom it removes the electrons from that atom.

#### Question 21.8

• The particle whose ionizing power is large will lose all energy in a very short time interval.
• While particle with less ionize power can move to a larger distance since it will generate less number of ions.

#### Question 21.9

• These are some information given by the Wilson cloud chamber.
• The track for alpha particles is straight, continuous, and have large area due to the large mass and high ionizing power.
• For beta particles track is thin, short, and discontinuous due to less weight and less value of ionizing energy than the alpha particle.
• There is no specific track for gamma rays due to high penetrating power and lesser ionizing energy.

#### Question 21.10

• For the detection of alpha particles, Geiger Muller has thin window for the detection of alpha particles.
• Since this gives the easiest path for less penetrating alpha particles to go in the tube.
• While to detect gemma particles there is no need of any window because the penetration speed of gemma rays is high.

#### Question 21.11

• Its working principle based on the creation of pairs of electrons and holes after absorption of energy from the incident photons of light.
• Due to these carriers’ current flows used in detection applications.

#### Question 21.12

• The amount of mass of nuclear fuel that is enough to receive mostly neutrons for a self-sustained fission chain reaction.

#### Question 21.13

• For the generation of electricity, this is cheap.
• These are permanent.
• Smoke does not generate through them.
• It exists in large quantities.

• These are expensive.
• These are not permanent and their life is less.
• Smoke will generate through them.
• It does not exist in large quantities.

• The radiation emitted through nuclear power are dangerous.

#### Question 21.14

• For fusion reaction, there is a need of high energy and temperature of million degrees that can be possible to create.

#### Question 21.15

• As there is no radioactive fossils products for a fusion reaction, so it does not hazard.
• As compared to fission reaction energy given by the fusion reaction is larger.

#### Question 21.16

• The radiation generated by the cosmic rays and due to the existence of radioactive materials below the crest of the earth are known as background radiation.

#### Question 21.17

• The alpha particles will damage more blood cells than the beta particles due to large ionizing energy.
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#### Question 21.18

• As you know that.
• ‘D’ is absorbed dose. Its formula is.

D= Energy / Mass

E = D x Mass

• As the mass of a complete body is large than the mass of hand, so for one (mGY) more energy will be absorbed.

#### Question 21.19

• To detect the position of an element through the mechanical system, biological and chemical systems radioisotopes are used.
Medicine:
• For finding the proper working of the thyroid gland radioactive iodine is used.

#### Question 21.20

• Radiotherapy removes the cells of cancer by distracting their DNA. For this therapy, high energy radiation is used to distract the cells.
• Gamma rays having cobalt 60 are used in the treatment of cancer.
• Radioactive iodine-131 is used to remove thyroid gland cancer.
• For the treatment of skin cancer, phosphorous 32 is used.

#### Related Posts

So, friends, it is the detailed post 2nd Year Physics Chapter 20 Solved Questions if you have ay question about this post ask in comment. Thanks for reading. See you in the next post.