Chapter 31: Q. 54 (page 903)

For a science project, you would like to horizontally suspend an $8.5$ by $11$ inch sheet of black paper in a vertical beam of light whose dimensions exactly match the paper. If the mass of the sheet is $1.0 g$ , what light intensity will you need $?$

Short Answer

Expert verified

Needed light intensity is $4.9 \times 10^{7} W / m^{2}$ .

Step by step solution

Calculation for Area and force

Area is,

$A = 8.5 inch \times 11 inch$

$A = 0.215 m \times 0.279 m$

$A = 0.059 m^{2}$

Force is,

$F = m \times g$

localid="1650002776253" $F = 1 \times 10^{- 3} Kg \times 9.8$

$F = 9.8 \times 10^{- 3} N$

Calculation for power

If an item absorbs energy over a time interval $∆ t$ , the momentum will vary as follows:

$ΔP = \frac{energy absorbed}{c}$

$F = \frac{ΔP}{Δt} = \frac{\frac{energy}{Δt}}{c}$

$F = \frac{\overset{}{P}}{c}$

$P = F \times c$

$P = 9.8 \times 10^{- 3} N \times 3 \times 10^{8} m / s$

$P = 29.4 \times 10^{5} W$

Calculation for intensity

Intensity is,

$I_{avg} = \frac{P}{A}$

$I_{avg} = \frac{29.4 \times 10^{5} W}{0.059 m^{2}}$

$I_{avg} = 4.9 \times 10^{7} W / m^{2}$

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For a science project, you would like to horizontally suspend an $8.5$ by $11$ inch sheet of black paper in a vertical beam of light whose dimensions exactly match the paper. If the mass of the sheet is $1.0 g$ , what light intensity will you need $?$

Short Answer

Step by step solution

Calculation for Area and force

Calculation for power

Calculation for intensity

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For a science project, you would like to horizontally suspend an8.5 by 11 inch sheet of black paper in a vertical beam of light whose dimensions exactly match the paper. If the mass of the sheet is 1.0g, what light intensity will you need?

Short Answer

Step by step solution

Calculation for Area and force

Calculation for power

Calculation for intensity

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Physics Textbooks

Mechanics and Materials

Electricity and Magnetism

Wave Optics

Nuclear Physics

Engineering Physics

Dynamics

Study anywhere. Anytime. Across all devices.

For a science project, you would like to horizontally suspend an $8.5$ by $11$ inch sheet of black paper in a vertical beam of light whose dimensions exactly match the paper. If the mass of the sheet is $1.0 g$ , what light intensity will you need $?$