# Difference in depth between the swimmer and its image

A plane mirror is placed on the level bottom of a swimming pool, which holds water to a depth of 3 m. A swimmer is located 2.0 m above the mirror. An observer above the water looks vertically downward at the swimmer and its image in the mirror. What is the apparent difference in depth between the swimmer and its image in the mirror?

I used the formula h'=h(1/(4/3)) where h' is the apparent depth as seen by the observer and h as the actual depth of the object.

the h' of the swimmer is 0.75 m while the mirror is 2.25 m.

I subtracted the 0.75 to 2.25 to get the distance between those 2. And I got 1.5.

Since it's a plane mirror, the image distance is only twice the object distance from the mirror.

My answer is 3 m..

is it correct?

## Answers and Replies

tiny-tim
Science Advisor
Homework Helper
Hi jsalapide! … I used the formula h'=h(1/(4/3)) where h' is the apparent depth as seen by the observer and h as the actual depth of the object.

the h' of the swimmer is 0.75 m while the mirror is 2.25 m.

I subtracted the 0.75 to 2.25 to get the distance between those 2. And I got 1.5.

Since it's a plane mirror, the image distance is only twice the object distance from the mirror.

My answer is 3 m..

is it correct?

Yup! (but a bit longwinded … you could have said the actual distance is 4m, then apply the h' formula, which reduces it to 3m … you don't need to find the 0.75 )