A group of hikers hears an echo 2.90 s after shouting. How far away is the mountain that reflected the sound wave? (Assume the speed of sound is 341 m/s.)

494.45 m.

Explanation:

Echo: This is the sound heard after the reflection of sound wave in a plain surface.

v = 2x/t Equation 1

Where v = velocity of sound in air, x = distance between the mountain and the hikers, t = time to hear the echo.

making x the subject of the equation,

x = vt/2 Equation 2

Given: v = 341 m/s, t = 2.9 s.

Substitute into equation 2

x = 341(2.9)/2

x = 494.45 m.

Hence the mountain is 494.45 m far away

explanation:

v=uf/(u-f)

= 5.-10/(5+10) convex lens has negative focal length

small = small current large mag large current