Rays from the sun are focused by a lens of diameter 5 cm on to a block of ice and 10 g of ice

step 1 Hello students in this question rays from the sun are focused on the lens of diameter D equals t

Rays from the sun are focused by a lens of diameter 5 cm on...

Rays from the sun are focused by a lens of diameter $5 \mathrm{~cm}$ on to a block of ice and $10 \mathrm{~g}$ of ice is melted in 20 min. Therefore the heat from the sun reaching the earth per min per square centimetre is (Latent heat of ice $L=80 \mathrm{cal} \mathrm{g}^{-1}$ ) (a) $2.04 \mathrm{cal}$ (b) $0.51 \mathrm{cal}$ (c) $4.08 \mathrm{cal}$ (d) $3.02 \mathrm{cal}$

Rays from the sun are focused by a lens of diameter $5 \mathrm{~cm}$ on to a block of ice and $10 \mathrm{~g}$ of ice is melted in 20 min. Therefore the heat from the sun reaching the earth per min per square centimetre is (Latent heat of ice $L=80 \mathrm{cal} \mathrm{g}^{-1}$ )
(a) $2.04 \mathrm{cal}$
(b) $0.51 \mathrm{cal}$
(c) $4.08 \mathrm{cal}$
(d) $3.02 \mathrm{cal}$

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Key Concepts

Energy Conservation Principle

The conservation of energy principle states that energy cannot be created or destroyed but only transformed from one form to another. In this context, the energy that melts the ice is supplied by sunlight, and equating the energy absorbed by the ice to the solar energy collected helps in quantifying the intensity of the radiation.

Radiation Intensity

Radiation intensity, or flux, denotes the amount of energy received per unit area per unit time. It is a crucial concept when assessing the effectiveness of an energy focusing system, such as a lens concentrating sunlight, in delivering sufficient energy to achieve a specific physical effect like melting ice.

Latent Heat

Latent heat is the amount of energy required to change the state of a substance without changing its temperature. In phase changes such as melting, this concept allows us to determine how much energy is absorbed or released per unit mass of the substance during the transformation.

Area Calculation for Circular Apertures

Determining the area of a circular opening, like that of a lens, is essential because it quantifies the effective cross-sectional area through which energy is collected or transmitted. This is typically calculated using the formula ?r², where r is the radius of the circle.

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