8/10/2019 Half Yearly Revision Imarks

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HALF YEARLY REVISION I MARKS: 60

LESSON: DUAL NATURE OF MATTER AND RADIATION

I.CHOOSE THE BEST ANSWER: 101=10

1. The work function of a photoelectric material is 3.3 eV. The thresholdfrequency will be equal to

a) 8x1014Hz b) 8x1010Hzc) 5x10 20Hz d) 4x1014Hz

2. For a given frequency of incident light, the stopping potential -------------

with respect to the intensity of lighta) Decreases b) increases

c) Does not change d) become zero?

3. The radiation falling on the photocell in burglar alarm isa) IR rays b) UV rays

c) X-rays d) - rays

4. In a photo emissive cell, the surface of the cathode is coated with

a) Silver chloride b) Lead oxide

c) Silver bromide d) Cesium oxide

5. The resolving power of a microscope is -------- to the wavelength ofradiation used

a) Directly proportional b) Inversely proportional

c) Directly proportional to the square

d) inversely proportional to the square

6. In electron microscope, the wavelength obtained by an electron

accelerated by a potential 60000 V is

a) 3x108m b) 5 x1012mc) 5x10-12m d) 3x10-8m

7. The rest mass of an electron is 9.1x10-31kg. What will be its mass if it

moves with 4/5thof the speed of light?a) 10.23 x10-31kg b) 7.89 x10-31kg

c) 12.36 x 10-31kg d) 15.16 x 10-31kg

8. X-rays are not converged by glass lenses because the refractive index forglass with respect to Xrays is

a) < 1 b) =1 c) >1 d) = 09. The length of metre rod traveling with a velocity of 0.6 c is

a) 0.08 m b) 0.8 m c) 0.64 m d) 0.36 m

10. In Newtons mechanics which of the following is treated as absolute?

a) Mass b) timec) length & space d) all the above

II. ANSWER THE FOLLOWING: (ANY 5) 53=15

1. What is meant by special theory of relativity?

2. If a body moves with the velocity of light, what will be its mass?

Comment on your result.3. Define work function.

4. Define cut off potential?5. Define frame of reference and what are their types?

6. The work function of zinc is 6.8 x 10-19J. What is the threshold frequency

for emission of photoelectrons from zinc?7. Find the accelerating potential of the electron, when its de Broglie

wavelength is 1A.

III.ANSWER THE FOLLOWING: (ANY 7)

NOTE: 8 AND 9 COMPULSORY

1. Establish Einsteins mass energy equivalence, E = mc2.

2. Derive Einsteins Photo electric equation?

3. Explain photoelectric effect? State the laws of photo electric

emission?

4.

Explain length contraction with an example5. Explain the wave mechanical concept of atom.

6.

Derive an expression for de Broglie wavelength of an electron?

7.

What are the applications of photo cell?

8. For an observer imagined to be moving at a speed of 36x106 km/hr.,

length of the rod measures 1 m. Find the length of the rod as

measured by a stationary observer.OR

A proton is moving at a speed of 0.900 times the velocity of light.

Find its kinetic energy in joules and

MeV.9. Ultra violet light of wave length 2271 from a source irradiates a photo -

cell which is made of molybdenum metal. If the stopping potential is 1.3

volt, calculate the work function of the metal. How would the photo cellrespond to a high intensity (105Wm-2) red light of wavelength 6328

produced by HeNe Laser?OR

The photoelectric threshold wavelength of a metal is 5000 . Find (i) the

work function in electron volts and (ii) the kinetic energy of the

photoelectrons in electron volts, ejected by the light of wave length 4000 .