Question

A 0.60 mW laser produces a beam of light with a diameter of 1.1 mm . Part A What is the average intensity of this beam?

Part B At what distance does a 130 W lightbulb have the same average intensity as that found for the laser beam in part (a)? (Assume that 5.0% of the bulb's power is converted to light.)

Answer 1

The average intensity of this beam and the distance are 631.4 w/m² and 2.86 cm.

Step-by-step explanation:

Given that,

Power = 0.60 mW

Diameter = 1.1 mm

(A). We need to calculate the average intensity of this beam

Using formula of intensity

`I=(P)/(A)`

Put the value into the formula

`I=(0.60*10^(-3))/((\pi(1.1*10^(-3))^2)/(4))`

`I=631.4\ W/m^2`

(B). We need to calculate the distance

Given that,

Power = 130 W

5% of 130 W is 6.5 w

Using formula of intensity

`I=(P)/(A)`

Put the value into the formula

`631.4=(6.5)/(4\pi (r)^2)`

`r^2=(6.5)/(4\pi*631.4)`

`r=√(0.000819)`

`r =0.0286\ m=2.86\ cm`

The distance is 2.86 cm.

Hence, The average intensity of this beam and the distance are 631.4 w/m² and 2.86 cm.