Discovery of Proton Canal Rays - UNSOLVED PRACTICE SET

Q7. What are canal rays? How are they produced in a discharge tube? Name the scientist who discovered them.

Q8. Why are canal rays called "canal rays" or "anode rays"? Explain the origin of these names with reference to the experimental setup.

Q9. Your teacher shows you two discharge tubes — one producing cathode rays and another producing canal rays. She asks you to identify one key difference between them based on their charge. How would you answer?

Q10. The e/m value of canal rays is different for different gases, while the e/m value of cathode rays is the same regardless of the gas. Explain why this difference exists.

Q11. How did the study of canal rays lead to the discovery of the proton? What was the significance of using hydrogen gas in these experiments?

Q12. Compare cathode rays and canal rays on the basis of: (i) charge, (ii) direction of deflection in electric field, (iii) e/m value, and (iv) origin in the discharge tube.

Q13. With the help of a labelled diagram, describe Goldstein's experiment that led to the discovery of canal rays. Explain the observations, the conditions required, and how these experiments contributed to the discovery of the proton.

Q14. A student reads that canal rays were discovered before the proton was identified. He wonders why it took time to identify the proton from canal rays. Help the student by explaining:

(a) Why canal rays from different gases have different e/m values.

(b) How the use of hydrogen gas simplified the identification.

(c) The relationship between the hydrogen ion (H⁺) and the proton.

(d) Why the proton is considered a fundamental particle of all atoms.

Q15. "The discovery of canal rays and the proton completed the picture of the positively charged part of the atom." Discuss this statement by explaining: (i) what was known about the atom before this discovery, (ii) how canal ray experiments revealed the existence of positive particles, (iii) why the proton is considered the nucleus of hydrogen, and (iv) how this discovery influenced Rutherford's later gold foil experiment.

Q16. In a canal ray experiment using hydrogen gas, the following data was obtained:

Charge of the particle = 1.6 × 10⁻¹⁹ C

e/m ratio = 9.58 × 10⁷ C/kg

(a) Calculate the mass of the hydrogen ion (proton).

(b) Compare this mass with the mass of an electron (9.1 × 10⁻³¹ kg). How many times heavier is a proton than an electron?

(c) If a beam of canal rays contains 10¹² protons, calculate the total charge and total mass of the beam.

(d) Why is the proton considered the fundamental positive particle, while the hydrogen ion is considered a specific case?

Q17. A discharge tube contains different gases, and the e/m values of the resulting canal rays are measured:

Table

Gas e/m value (C/kg)

Hydrogen 9.58 × 10⁷

Helium 4.79 × 10⁷

Oxygen 5.99 × 10⁶

Nitrogen 6.84 × 10⁶

(a) Which gas produces canal rays with the highest e/m value? What does this tell you?

(b) The e/m value for helium is exactly half that of hydrogen. Explain why.

(c) Calculate the mass of the canal ray particle from oxygen gas. (Charge = 1.6 × 10⁻¹⁹ C)

(d) How does this data support the idea that canal rays are positively charged ions of the gas used?

Q18. A mass spectrometer is a modern instrument that separates ions based on their mass-to-charge ratio, similar to the principle of canal ray experiments.

(a) Explain how a mass spectrometer works, drawing an analogy to canal ray experiments.

(b) If a sample contains ions with masses 1 u, 2 u, and 16 u, and all have a charge of +1, sketch the expected pattern on the detector screen.

(c) A mass spectrometer is used to analyse drinking water for heavy metal contamination. Why is this important for public health in India?

(d) If a water sample shows a peak at 208 u, which heavy metal might be present? (Hint: Think about common water pollutants in India).