2. With the help of diagram explain the Edison s discovery of thermionic emission. Mention the observations and the conclusion.

Size: px

Start display at page:

Download "2. With the help of diagram explain the Edison s discovery of thermionic emission. Mention the observations and the conclusion."

Dwain Norris
6 years ago
Views:

1 Work Sheet Explain the following terms i) Bound Electrons ii) Conduction/free electrons iii) Work function iv) Thermionic emission 2. With the help of diagram explain the Edison s discovery of thermionic emission. Mention the observations and the conclusion.

2 Work Sheet Write and explain the factors affecting the rate of thermionic emission. 2. What are the requisites for a good electron emitter. 3. Draw a labeled diagram of a Hot Cathode ray tube.

3 Work Sheet Write the principle of the Hot Cathode Ray Tube. 2. Write in short about the three major parts of the Hot Cathode Ray Tube i) Electron Gun ii) Deflecting System iii) Fluorescent Screen. 3. Write the uses of Hot Cathode Ray Tube.

4 Work Sheet Define Radioactivity. 2. Draw a diagram to show the deflection of radioactive radiations in an electric field. 3. Write five properties each of alpha particles, beta particles and gamma radiations.

5 Work Sheet Write the equations of alpha, beta and gamma emissions, also write an example for each. 2. Write the uses of radio isotopes for medical, scientific and industrial use. 3. Write the harmful effects and safety precautions for radioactive radiations. 4. What do you mean by background radiations.

6 Work Sheet - 6 Thermionic emission 1.i) Name the particles given out during radio active decay. ii) Show by equations, the effect on proton number Z and mass number A of the parent nucleus brought about by the two types of radioactive decay. [2001] [4] 2. The following diagram is a simplified version of a hot cathode ray tube The figure is a simplified version of cathode ray tube. Answer the following [4] (i) What is the amount of charge of the charged particles emitted? (ii) What is the approximate value of V 1? (iii) What is the approximate value of V 2? (iv) What will happen to the charged particle when it passes through the magnetic field? 3. i) Which radiation or particle from radioactivity produces maximum biological damage? ii) State three precautions that must be taken while handling a radioactive source. [2]

7 Work Sheet - 7 Thermionic emission 1. i) Mention two possible sources of background radiation. [2002] [2] ii) An elemeny X changes to another element Y with the emission of beta particles. Write down the equation showing changes in the nucleus. Take the proton number and mass number of X, as Z and A respectively. [2] 2. a) State briefly two uses of a cathode ray tube. [2002] [2] b) Describe briefly, two properties each of alpha particles and gamma radiations. [4] 3. A mass of lead is embedded in a block of aluminium( 2mm thick). Radiations from a radioactive source incident on the side of the block produce a shadow on a fluorescent screen placed beyond the block. The shadow of the block of aluminium is fainter than the shadow of lead. Give the reason for this difference. [2003] [2] 4.a) State two factors on which the rate of emission of thermions depends. [2003] [2] b) The isotope of 92 U 238 decays by alpha emission to an isotope of Thorium(Th). The thorium isotope decays by beta emission to an isotope of Protactanium(Pa). Write down the equations to represent these two nuclear changes. [4]

8 Work Sheet - 8 Thermionic emission 1. Draw a cathode ray tube consisting of a heater, a cathode, a cylindrical anode and a deflecting system. Show how you will connect a low tension battery of 6V and a high tension one of 1000V to the electrodes of the tube. [4] 2. Define the term work function of a metal. 3. Mention two common properties of gamma radiations and visible light. [2004] [2] 4. a) Name the radiations which have the least penetrating power. [1] b) i) Give one difference between chemical change and nuclear change. [1] ii) How is a cathode ray tube used to convert an electrical signal into a visual signal. [2] c) Copy and complete the following nuclear equations by filling in the correct values in the blanks. 92P P P P 3 [3] 5. 1eV =? [2] 6. Distinguish between alpha, beta and gamma radiations in terms of frequency, charge, speed and penetrating power. [4]

9 Work Sheet - 9 Thermionic emission 1. Draw a diagram to show the charge of alpha, beta and gamma radiations. [3] 2. How many alpha and beta particles are emitted when Uranium nucleus 92 U 238 decays to Lead 82 Pb 206? [2005] [2] 3. a) Mention two important precautions that should be taken while handling radioactive materials. State one use of radioactive isotopes. [3] b) Draw a labeled diagram of a hot cathode ray tube. Why are materials of low work function preferred as thermionic cathode materials? [4]

RADIOACTIVITY. An atom consists of protons, neutrons and electrons.

RADIOACTIVITY. An atom consists of protons, neutrons and electrons. RADIOACTIVITY An atom consists of protons, neutrons and electrons. - Protons and neutrons are inside the nucleus - Electrons revolve around the nucleus in specific orbits ATOMIC NUMBER: - Total number