In the photoelectric effect, if the frequency of incident light is doubled, what happens to the kinetic energy of emitted electrons? (2020)
Practice Questions
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Q1
In the photoelectric effect, if the frequency of incident light is doubled, what happens to the kinetic energy of emitted electrons? (2020)
It doubles
It quadruples
It remains the same
It becomes zero
Kinetic energy (KE) = hf - φ. If frequency is doubled, KE increases by a factor of 4.
Questions & Step-by-step Solutions
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Q
Q: In the photoelectric effect, if the frequency of incident light is doubled, what happens to the kinetic energy of emitted electrons? (2020)
Solution: Kinetic energy (KE) = hf - φ. If frequency is doubled, KE increases by a factor of 4.
Steps: 7
Step 1: Understand the photoelectric effect. It describes how light can cause electrons to be emitted from a material.
Step 2: Know the formula for kinetic energy (KE) of emitted electrons: KE = hf - φ, where h is Planck's constant, f is the frequency of the incident light, and φ is the work function of the material.
Step 3: If the frequency (f) of the incident light is doubled, we replace f with 2f in the formula: KE = h(2f) - φ.
Step 4: Simplify the new equation: KE = 2hf - φ.
Step 5: Compare the new kinetic energy (2hf - φ) with the original kinetic energy (hf - φ).
Step 6: Notice that the new kinetic energy is twice the original kinetic energy plus the same work function: KE_new = 2(KE_original + φ) - φ.
Step 7: This means that the kinetic energy increases, and specifically, it increases by a factor of 4 because the energy is proportional to the square of the frequency.
