Question 1

Which experiment provided the first evidence for the existence of the electron, and what was the key observation?

Accepted Answer

Thomson's cathode ray tube experiment; observation of cathode rays being deflected by electric and magnetic fields

Question 2

According to the Rutherford model of the atom, what is the main difference compared to Thomson's 'plum pudding' model?

Accepted Answer

The atom is mostly empty space with a dense, positively charged nucleus

Question 3

Which of the following best describes the Bohr model of the atom?

Accepted Answer

Electrons move in fixed orbits around the nucleus with quantized energies

Question 4

A photon has an energy of $5.25 	imes 10^{-19}$ J. What is its wavelength in meters? (Use $h = 6.626 	imes 10^{-34}$ Js and $c = 3.00 	imes 10^8$ m/s)

Accepted Answer

$3.78 	imes 10^{-7}$ m

Question 5

Which region of the electromagnetic spectrum has the highest energy photons?

Accepted Answer

Gamma rays

Question 6

What is the relationship between the wavelength ($\lambda$) and frequency ($
u$) of light?

Accepted Answer

$c = \lambda 
u$

Question 7

Which phenomenon could NOT be explained by the wave model of light, leading to the development of the quantum model?

Accepted Answer

Photoelectric effect

Question 8

A metal requires a minimum frequency of $1.09 	imes 10^{15}$ s$^{-1}$ for electron emission. What is the corresponding threshold wavelength?

Accepted Answer

$2.75 	imes 10^{-7}$ m$

Question 9

Which statement about the photoelectric effect is correct?

Accepted Answer

Electrons are ejected only if the light frequency exceeds a threshold value, regardless of intensity

Question 10

Calculate the energy required to ionize a hydrogen atom from its ground state ($n=1$) to $n=\infty$. Use $E_n = -2.1799 	imes 10^{-18} \frac{1}{n^2}$ J.

Accepted Answer

$2.1799 	imes 10^{-18}$ J

Question 11

Which electron transition in a hydrogen atom emits a photon with the highest energy?

Accepted Answer

From $n=2$ to $n=1$

Question 12

What is the de Broglie wavelength of an electron (mass $9.11 	imes 10^{-31}$ kg) moving at $2.00 	imes 10^6$ m/s? ($h = 6.626 	imes 10^{-34}$ Js)

Accepted Answer

$3.63 	imes 10^{-10}$ m

Question 13

Which of the following best explains why only certain colors are observed in the emission spectrum of hydrogen?

Accepted Answer

Electrons can only occupy specific energy levels, so only certain transitions are allowed

Question 14

A photon is absorbed by a hydrogen atom, causing an electron to move from $n=1$ to $n=3$. What is the energy of the absorbed photon? ($E_n = -2.1799 	imes 10^{-18} \frac{1}{n^2}$ J)

Accepted Answer

$1.937 	imes 10^{-18}$ J

Question 15

Which of the following statements about the dual nature of light is correct?

Accepted Answer

Light exhibits both wave-like and particle-like properties

Question 16

Which transition in the hydrogen atom corresponds to the emission of ultraviolet light?

Accepted Answer

Transitions ending at $n=1$ (Lyman series)

Question 17

If an electron in a hydrogen atom falls from $n=4$ to $n=2$, what type of electromagnetic radiation is emitted?

Accepted Answer

Visible light

Question 18

Which of the following best describes the significance of Planck's constant ($h$) in quantum theory?

Accepted Answer

It relates the energy of a photon to its frequency

Question 19

Which of the following is a real-world application of the photoelectric effect?

Accepted Answer

Solar panels converting sunlight into electricity

Atomic Structure, Light, and Quantum Theory: Study Notes

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