# MODERN PHYSICS Quiz for Fun & Quiz Competition Practice 2

## Results

### #5. The unit of Planck’s constant is

Explanation is given below

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## MODERN PHYSICS Quiz Explanations

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1. The energy of an atom is E = -13.6 z2/n2

For He+, n = 2, z = 2.

Hence the enrgy, E = -13.6 eV.

2. Roger Penrose won the Nobel Prize 2020 for the study of black holes and how it is a “robust” prediction of the General theory of relativity of Albert Einstein.

For more about black holes, see here

3. Velocity of electron in the first Bohr orbit is = c/137, where c = speed of light in free space

So, speed of electron with respect to that of light is (c/137)/c = 1/137

4. Energy, E = -13.6 (z2/n2)

For lithium, z = 3, so n must be 3 to make it equal to the ground level energy of hydrogen.

5. E = hf

so, h = E/f

= joule/hertz

= joule.second

Quiz By Som Abhisek.

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### MODERN PHYSICS Quiz

1. The energy of an atom in the first excited state is -13.6 eV. It may be

a. He+ ()

b. Li++

c. hydrogen

d. uranium

2. Roger Penrose won Nobel prize 2020 for his contribution in the study of

a. particle physics

b. black hole physics()

c. analog electronics

3. The velocity of the electron in the first Bohr orbit as compared to that of light is about

a. 1/300

b. 1/500

c. 1/187

d. 1/137 ()

9. Which energy state of Li++ has the same energy as that of hydrogen in the ground level?

a. n = 1

b. n = 3 ()

c. n = 2

d. n = 4

5. The unit of Planck’s constant is

a. joule.metre

b. joule.second ()

c. joule/second

d. newton.second