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Light with an average flux of 20 W/cm2 falls on a non reflecting surface at normal incidence having surface area 20 cm2. The energy received by the surface during time span of 1 minute is :

This question was previously asked in
NEET 2020 Official Paper (Held On: 13 September, 2020)
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  1. 24 × 103 J
  2. 48 × 103 J
  3. 10 × 103 J
  4. 12 × 103 J

Answer (Detailed Solution Below)

Option 1 : 24 × 103 J
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Detailed Solution

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Concept:

The waves which have both electric as well as magnetic field such that electric and magnetic fields are perpendicular to each other and also to direction of propagation is called as electromagnetic waves.

Calculation:

Intensity of light =20 W/cm2 

Area = 20 cm2

Time = 1 minute = 60 seconds

Energy received = Intensity × Area × Time

= 20 × 20 × 60

= 24 × 103 J

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