1. 10×10³ J 2. 12×10³ J 3. 24×10³ J 4. 48×10³ J

Answer: 3. 24×10³ J Energy received = flux × area × time. E=20\ W/cm²×20\ cm²×60\ s=24000\ J=24×10³\ J Answer: option 3.

Light with an average flux of 20 W/cm^2 falls on a non-reflecting surface at normal incidence having surface area 20 cm^2. The energy received by the surface during time span of 1 minute is :

1. $10\times10^3$ J

2. $12\times10^3$ J

3. $24\times10^3$ J

4. $48\times10^3$ J

Doubtly Asked 30 Oct 2026 NEET UG 2020 Practice test neet Save WhatsApp Report

Best answer

Answer: 3. $24\times10^3$ J

Energy received = flux $\times$ area $\times$ time.

$$E=20\ \text{W/cm}^2\times20\ \text{cm}^2\times60\ \text{s}=24000\ \text{J}=24\times10^3\ \text{J}$$

Answer: option 3.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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