Two people are talking at a distance of 3.0 m from where you are, and you measure the sound intensity as 1.1'10 W/m. Another student
is 4.0 m away from the talkers. Calculate a reasonable estimate for the
sound intensity that the other student measures.
A) 62' 10-8 W/m2
B) 1.5'10-7 W/m2
8.3' 10-8 W/m2
D) 7.8'10-7 W/m2

The sound intensity that the other student measure, I₂ is expected to be;

A) 6.2 × 10⁻⁸ W/m²

Explanation:

The measure of sound intensity is given by the following formula;

Where;

I = The intensity

R = The radius

P = The power of the sound

Whereby we have;

The distance of the two people talking, R₁ = 3.0 m

The measure of the sound intensity, I₁ = 1.1 × 10⁻⁷ W/m² (from an online source)

The distance of the other student from the two people talking, R₂ = 4.0 m

Therefore, the estimate of the sound intensity, I₂, is given as follows;

I₂ = 6.1875 × 10⁻⁸ W/m²

∴ The sound intensity that the other student measure, I₂ ≈ 6.2 × 10⁻⁸ W/m²

d

explanation:

v=uf/(u-f)

= 5.10/(5-10) convex lens has positive focal length

=50/-5

=-10 cm (formed at other side)