Concepts Of Physics MCQ Edition [Volume 1]
- Exam
- Concepts Of Physics MCQ Edition [Volume 1]
- Subject
- Physics
- Chapter
- Geometrical Optics
Concepts Of Physics MCQ Edition [Volume 1] · Physics · Geometrical Optics
A 1.00 m long pole stands half-dipped in a swimming pool where the...
A long pole stands half-dipped in a swimming pool where the water level is above the bed. The refractive index of the water is , and sunlight strikes at an angle of 45^{}^{{}^{\circ}} with the vertical. Determine the length of the pole's shadow on the bed.
Options
- A
- B
- C
- D
Correct answer
D.
Step-by-step solution
The total length of the pole is . Since it is half-dipped in the pool, the length of the pole above the water surface is and the length below the water surface is .
The sunlight strikes at an angle of 45^{}^{{}^{\circ}} with the vertical. The shadow cast by the portion of the pole above the water on the water surface has a length given by:
x_1 = 50 \tan 45^{}^{{}^{\circ}} = 50 \text{ cm}
The light ray from the tip of the pole strikes the water surface at an angle of incidence i = 45^{}^{{}^{\circ}}. Let the angle of refraction be . Applying Snell's law at the air-water interface:
\sin 45^{}^{{}^{\circ}} = 1.33 \sin r
Taking , we get:
The tangent of the angle of refraction is:
The refracted ray travels a vertical depth of to reach the bed of the pool. The horizontal distance covered by the refracted ray in the water is:
The total length of the pole's shadow on the bed is the sum of the horizontal distances:
Answer:
The sunlight strikes at an angle of 45^{}^{{}^{\circ}} with the vertical. The shadow cast by the portion of the pole above the water on the water surface has a length given by:
x_1 = 50 \tan 45^{}^{{}^{\circ}} = 50 \text{ cm}
The light ray from the tip of the pole strikes the water surface at an angle of incidence i = 45^{}^{{}^{\circ}}. Let the angle of refraction be . Applying Snell's law at the air-water interface:
\sin 45^{}^{{}^{\circ}} = 1.33 \sin r
Taking , we get:
The tangent of the angle of refraction is:
The refracted ray travels a vertical depth of to reach the bed of the pool. The horizontal distance covered by the refracted ray in the water is:
The total length of the pole's shadow on the bed is the sum of the horizontal distances:
Answer: