Q: Which formula gives the wavelength of maximum intensity for blackbody radiation according to Wien’s Law?

$$\lambda_{max} = \frac{2.90 \times 10^6$}{T} nm K$$

Question 1

A blacksmith heats a piece of iron until it glows orange, as seen in the image. According to Wien’s Law, what happens to the peak wavelength of the emitted radiation as the temperature increases?

Accepted Answer

The peak wavelength decreases, shifting the color toward blue.

Question 2

Which equation correctly describes the total power radiated by a blackbody per unit time?

Accepted Answer

$$\frac{dQ}{dt} = e\sigma AT^4$

Question 3

A blackbody at 2000 K radiates 100 W of power. If its temperature is increased to 4000 K, how much power does it radiate?

Accepted Answer

800 W

Question 4

Which of the following statements best explains the ultraviolet catastrophe?

Accepted Answer

Classical physics predicts infinite energy emission at short wavelengths, which is not observed experimentally.

Question 5

Which formula gives the wavelength of maximum intensity for blackbody radiation according to Wien’s Law?

Accepted Answer

$$\lambda_{max} = \frac{2.90 	imes 10^6$}{T} nm K$$

Question 6

Which of the following is NOT a prediction of Dalton’s atomic theory?

Accepted Answer

Atoms can be subdivided into smaller particles.

Question 7

Which experiment provided evidence that atoms have a small, dense, positively charged nucleus?

Accepted Answer

Rutherford’s gold foil experiment

Question 8

What is the main piece of evidence that persuaded J.J. Thomson that cathode rays are fundamental constituents of atoms?

Accepted Answer

They have the same charge-to-mass ratio for all cathode materials.

Question 9

Which of the following statements about X-rays is FALSE?

Accepted Answer

X-rays can be deflected by a magnetic field.

Question 10

In Thomson’s crossed-field experiment, the charge-to-mass ratio of the electron is given by which formula?

Accepted Answer

$$\frac{q}{m} = \frac{rB}{E}$$

Question 11

Which of the following best describes the result of Rutherford’s gold foil experiment?

Accepted Answer

Most alpha particles passed through the foil, but a few were deflected at large angles.

Question 12

Which of the following is a correct statement about atomic spectra?

Accepted Answer

Each element has its own characteristic spectrum that acts like a fingerprint for that element.

Question 13

Which type of radiation discovered by Becquerel can be stopped by a sheet of paper and was later shown to be $$\mathrm{He}^{2+}$$ ions?

Accepted Answer

Alpha rays

Question 14

Why is alpha radiation particularly dangerous if ingested or inhaled, despite being unable to penetrate skin?

Accepted Answer

It deposits all its kinetic energy in a small volume of tissue.

Question 15

Which of the following was NOT explained by classical physics by the early 20th century?

Accepted Answer

Why atoms have discrete spectra

Question 16

Which of the following is a property of cathode rays as discovered by Crookes and Thomson?

Accepted Answer

They are deflected by a magnetic field.

Question 17

What is the fundamental unit of electric charge as determined by Millikan’s oil-drop experiment?

Accepted Answer

$$e = 1.60 	imes 10$$^{-19}$$ C

Question 18

Which of the following best describes the structure of the atom according to Rutherford’s model?

Accepted Answer

A small, dense, positively charged nucleus surrounded by electrons in mostly empty space.

Question 19

Which of the following is a real-world application of the discovery of X-rays?

Accepted Answer

Medical imaging to view bones and internal structures.

The Failure of Classical Physics and the Birth of Modern Atomic Theory

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