The irradiance of light from a point source is 32 W m⁻² at a distance of 4.0 m from the source - Scottish Highers Physics - Question 15 - 2016

Using the information provided: At 4.0 m, I = 32 W m⁻²: $k = I imes r^2 = 32 imes (4.0)^2 = 32 imes 16 = 512$

Now, using the constant k to find the irradiance at 16 m: $I = \frac{k}{r^2} = \frac{512}{(16)^2} = \frac{512}{256} = 2.0 W m⁻²$

From the calculations, the irradiance at a distance of 16 m is 2.0 W m⁻². Therefore, the correct answer is: C 2.0 W m⁻²