AP EAMCET · PHYSICS · Dual Nature of Matter

In a photoelectric experiment, a monochromatic light is incident on the emitter plate $E$, as shown in the figure. When switch $S_1$ is closed and switch $S_2$ is open, the photoelectrons strike the collector plate $C$ with a maximum kinetic energy of $1 \mathrm{eV}$. If switch $S_1$ is open and switch $S_2$ is closed and the frequency of the incident light is doubled the photoelectrons strike the collector plate with a maximum kinetic energy of $20 \mathrm{eV}$. The threshold wavelength of the emitter plate is

A $5233.3 Å$
B $4133.3 Å$
C $4166.7 Å$
D $5336.7 Å$

Verified Solution

Answer & Solution

Correct Answer

(B) $4133.3 Å$

Step-by-step Solution

Detailed explanation

Let threshold frequency of emitter plate $=v_0$ Energy of photon in first case is $\mathrm{E}$. When switch $S_1$ is closed and switch $S_2$ is open, So, $E=h v_0+(5+1) \mathrm{eV}$ ...(i) For second case, when switch $S_1$ is open and switch $S_2$ is closed and…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

A body is projected horizontally from the top of a tower of height

180 m

with a velocity of

20 {ms}^{- 1}

. If acceleration due to gravity is

10 {ms}^{- 2}

then match the following.

List-I		List-II
$(A)$	Velocity of the body after $1$ second $($ in ${ms}^{- 1}$ )	(I)	$5$
$(B)$	Horizontal displacement of the body after $1$ second (in meters)	(ii)	$20$
$(C)$	Vertical displacement of the body after $1$ second (in meters)	(iii)	$10$
$(D)$	Vertical velocity of the body after $1$ second $($ in ${ms}^{- 1}$ )	(iv)	$22.4$

The correct answer is

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