Question

Assume the helium-neon lasers commonly used in student physics laboratories have power outputs of 0.250 mW. (a) If such a laser beam is projected onto a circular spot 3.00 mm in diameter, what is its intensity (in watts per meter squared)

Answer 1

35.4watts/m²

Step-by-step explanation:

Given the power output of helium-neon laser = 0.250mW = 0.250×10^-3watts (1milliwatts = 10^-3watts

Diameter of the circular spot projected by laser beam = 3.00mm = 0.003m

Area of the circular spot = πd²/4

Area of the circular spot = π(0.003)²/4

= 7.069×10^-6m²

Intensity of the laser = power output/area

Intensity of laser = 0.250×10^-3Watts/7.069×10^-6m²

= 0.0354×10^-3+6

= 0.0354×10^3

Intensity of laser = 35.4watts/m²

Answer 2

I=8.84W/m

Step-by-step explanation:

The intensity of light is defined as

`I=(P)/(A)`

P: power of light

A: area

In our case the region impacted by the laser is a circle, hence we have

`I=(0.250mW)/(\pi r^(2))=(0.250*10^(-3)W)/(\pi (3*10^(-3)m)^2)\\I=8.84(W)/(m)`

Hope this helps!!

regards