In bright light the pupil of a person is 2.5 mm across…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
In bright light the pupil of a person is mm across. In dim light it is mm across.
- What is the area of the pupil in bright light?
- What is the area in dim light?
- How many times more light does the dim light pupil let in, for the same brightness outside?
Need a reminder? The key ideaShow
The eyeball has three layers: the sclera (with the cornea), the choroid (with the ciliary body and the iris) and the retina. The lens is held by ligaments of the ciliary body. The aqueous humour lies in front of the lens, and the vitreous humour lies behind it. The retina has ganglion cells, bipolar cells and photoreceptor cells from inside to outside. The area of a circle is .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Widths: mm and mm.
Plan. Use for each width, then divide the areas.
Step 1. Bright light. square millimetres.
Step 2. Dim light. square millimetres.
Step 3. The factor. . The width is times larger, so the area is times larger.
Answer: square millimetres; square millimetres; times.
Check. The factor of the areas is the square of the factor of the widths.
Watch out. The area does not grow in the same ratio as the width.
More onHuman Body
Discussion (0)
Log in to join the discussion.
Loading…