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.

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

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

Advantage of Nuclear Power Fossil

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

Advantage of Fuel Generated Fossil

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

Disadvantage

• 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

Advantage:

• 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.

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

Radioactive Tracer:

• To detect the position of an element through the mechanical system, biological and chemical systems radioisotopes are used.

• 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.

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