Modern Physics

The maximum kinetic energy of emitted photoelectrons in the photoelectric effect is determined by the equation:

$%7BK_%7B%5Ctext%7Bmax%7D%7D%7D%3Dh%5Cnu-%5Cphi$

Where:

$h%20%3D$ Planck's constant ( $6.626%20%5Ctimes%2010%5E%7B-34%7D%5C%2C%5Ctext%7BJs%7D$ )
$%5Cnu%20%3D$ Frequency of the incident light
$%5Cphi%20%3D$ Work function of the metal

The frequency $%5Cnu$ can be related to the wavelength $%5Clambda$ using:

$%5Cnu%3D%5Cdfrac%7Bc%7D%7B%5Clambda%7D$

Given $%5Clambda%3D400%5C%2C%5Ctext%7Bnm%7D%3D400%5Ctimes10%5E%7B-9%7D%5C%2C%5Ctext%7Bm%7D$ , and the speed of light $c%3D3%5Ctimes10%5E8%5C%2C%5Ctext%7Bm%2Fs%7D$ , we find $%5Cnu$ as:

$%5Cnu%3D%5Cdfrac%7B3%5Ctimes10%5E8%7D%7B400%5Ctimes10%5E%7B-9%7D%7D%3D7.5%5Ctimes10%5E%7B14%7D%5C%2C%5Ctext%7BHz%7D$

The energy of the photons is obtained by:

$E_%7B%5Ctext%7Bphoton%7D%7D%3Dh%5Cnu$

Substituting the values:

$E_%7B%5Ctext%7Bphoton%7D%7D%3D6.626%5Ctimes10%5E%7B-34%7D%5Ctimes7.5%5Ctimes10%5E%7B14%7D%5Capprox4.97%5Ctimes10%5E%7B-19%7D%5C%2C%5Ctext%7BJ%7D$

Convert $E_%7B%5Ctext%7Bphoton%7D%7D$ to electronvolts (1 eV = $1.602%5Ctimes10%5E%7B-19%7D%5C%2C%5Ctext%7BJ%7D$ ):

$%5Capprox%20%5Cdfrac%7B4.97%5Ctimes10%5E%7B-19%7D%7D%7B1.602%5Ctimes10%5E%7B-19%7D%7D%5Capprox3.1%5C%2C%5Ctext%7BeV%7D$

The maximum kinetic energy $%7BK_%7B%5Ctext%7Bmax%7D%7D%7D$ is:

$%7BK_%7B%5Ctext%7Bmax%7D%7D%7D%3D3.1-%5Cphi%3D3.1-2.0%3D1.1%5C%2C%5Ctext%7BeV%7D$

Doubling the intensity of light increases the number of photons hitting the metal per second, but it does not change the energy per photon or the frequency of light. Therefore, the maximum kinetic energy of the emitted photoelectrons remains unchanged.

The correct answer is:

It remains the same.

About Modern Physics - BITSAT

Modern Physics is a vital chapter for BITSAT aspirants. Mastering the concepts covered in this chapter is essential for securing a top rank.

By rigorously practicing the previous year questions associated with this chapter, you can identify high-yield topics, understand the examiner's perspective, and boost your confidence during the actual exam.

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How to best use this analysis?

Review the topic breakdown to see which sub-topics within Modern Physics carry the most weight. Then, tackle the questions iteratively to solidify your understanding.

High-Yield Trend

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About Modern Physics - BITSAT

Frequently Asked Questions

Why focus on Modern Physics PYQs?

How to best use this analysis?

Modern Physics

High-Yield Trend

Chapter Questions 2 MCQs

Official Solution

Official Solution

About Modern Physics - BITSAT

Frequently Asked Questions

Why focus on Modern Physics PYQs?

How to best use this analysis?

Chapter Questions
2 MCQs