Atomic Structure - Result Question 5

5. Which of the graphs shown below does not represent the relationship between incident light and the electron ejected from metal surface?

(2019 Main, 10 Jan I)

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Answer:

Correct Answer: 5. (d)

Solution:

  1. For photoelectric effect,

(i) $KE=E-E_0$

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where,

$ \begin{aligned} KE & =\text { Kinetic energy of ejected electrons. } \\ E & =\text { Energy of incident light }=h \nu \\ E _0 & =\text { Threshold energy }=h v _0 \\ v & =\text { Frequency of incident light } \\ v _0 & =\text { Threshold frequency } \end{aligned} $

<img src=“https://temp-public-img-folder.s3.amazonaws.com/sathee.prutor.images/sathee_image/cropped_2024_01_16_b4fdca9f34924034e8d8g-042_jpg_height_270_width_356_top_left_y_370_top_left_x_519.jpg"width="270">

Slope $= \pm 1$, intercept $=-E_0$

So, option (a) is correct.

(ii) $KE$ of ejected electrons does not depend on the intensity of incident light.

<img src=“https://temp-public-img-folder.s3.amazonaws.com/sathee.prutor.images/sathee_image/cropped_2024_01_16_b4fdca9f34924034e8d8g-042_jpg_height_250_width_405_top_left_y_822_top_left_x_452.jpg"width="270">

So, option (b) is correct.

(iii) When, number of ejected electrons is plotted with frequency of light, we get

<img src=“https://temp-public-img-folder.s3.amazonaws.com/sathee.prutor.images/sathee_image/cropped_2024_01_16_b4fdca9f34924034e8d8g-042_jpg_height_270_width_424_top_left_y_1214_top_left_x_448.jpg"width="300">

So, option (c) is also correct.

(iv) $KE=h v-h v_0$

<img src=“https://temp-public-img-folder.s3.amazonaws.com/sathee.prutor.images/sathee_image/cropped_2024_01_16_b4fdca9f34924034e8d8g-042_jpg_height_264_width_356_top_left_y_1581_top_left_x_476.jpg"width="250">

Slope $=+h$, intercept $=-h v_0$. So, option (d) is not correct.