Question

Which of the following statements are correct, if the threshold frequency of caesium is $ 5.16 \times 10^{14} \, \text{Hz} $?

• A. When Cs is placed inside a vacuum chamber with an ammeter connected to it and yellow light is focused on Cs, the ammeter shows the presence of current.
• B. When the brightness of the yellow light is dimmed, the value of the current in the ammeter is reduced.
• C. When a red light is used instead of the yellow light, the current produced is higher with respect to the yellow light.
• D. When a blue light is used, the ammeter shows the formation of current.

Hint:

In the photoelectric effect, only light with a frequency greater than the threshold frequency can cause the ejection of electrons. Reducing light intensity reduces the current, but light with insufficient frequency (like red light) will not cause any emission of electrons.

Answer 1

The Correct Option is D

Electrons are emitted from a material via the photoelectric effect when illuminated by light exceeding a specific threshold frequency.
Option A: The application of yellow light, possessing a frequency above the threshold, to caesium results in electron ejection and subsequent current flow. This statement is validated. 
Option B: A reduction in the intensity of yellow light diminishes the photon count, consequently lowering the quantity of ejected electrons. This leads to a decrease in the ammeter's current. This statement is validated. 
Option C: Red light, with a frequency below caesium's threshold, lacks the requisite energy for electron ejection. Consequently, no current is generated. This statement is invalidated. 
Option D: Blue light, exhibiting a frequency greater than the threshold, will induce electron emission and generate current in the ammeter. This statement is validated. 
Therefore, the accurate selections are B, C, and D exclusively.