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The diagram shows light from a point source, S, spreading out as it gets further from S - Edexcel - GCSE Physics - Question 5 - 2013 - Paper 1
Question 5
The diagram shows light from a point source, S, spreading out as it gets further from S. The intensity of light passing through the surface which is 1 m from S is 2... show full transcript
Worked Solution & Example Answer:The diagram shows light from a point source, S, spreading out as it gets further from S - Edexcel - GCSE Physics - Question 5 - 2013 - Paper 1
Step 1
Complete the sentence by putting a cross (X) in the box next to your answer.
Answer
To determine the intensity of light at 2 m from the source, we can use the inverse square law for intensity, which states that intensity is inversely proportional to the square of the distance from the source:
Given that the intensity at 1m is 2.5 W/m², at 2m:
I_2 = rac{I_1 imes r_1^2}{r_2^2} = rac{2.5 imes (1)^2}{(2)^2} = rac{2.5}{4} = 0.625 ext{ W/m²}
Thus, the correct answer would be D (2.5 × 4) equals the constant intensity at that distance.
Step 2
Calculate the power of the light passing through the surface which is 1 m from S.
Answer
Power can be calculated using the formula:
Given:
- Intensity (I) = 2.5 W/m²
- Area (A) = 0.2 m²
Calculating the power:
Therefore, the power of the light passing through the surface which is 1 m from S is 0.5 W.