Question

2.00 W/m2 passes through the pupil of one of your eyes and eventually falls on your retina. The radius of the pupil is controlled by the iris. In a human eye, the radius of the pupil can vary from about 1.0 mm to about 3.5 mm. The area of the opening can be calculated from pi (3.1416) times the radius squared. If your pupil is open to a radius of 2.5 mm, how much light energy passes through in one minute? Give your answer in kilojoules.

Answer 1

Answer:

(2.357 × 10⁻³) J = (2.357 × 10⁻⁶) KJ

Explanation:

Power = flux × (cross sectional area)

Q = q × A

Power = Q = ?

Flux = q = 2.00 W/m²

Cross sectional Area of the eye = A = πr²

r = radius of the eye at the moment that the calculation is required = 2.5 mm = 0.0025 m

A = πr² = π(0.0025)² = 0.0000196428 m²

A = (1.964 × 10⁻⁵) m²

Q = q × A

Q = 2 × 1.964 × 10⁻⁵

Q = (3.929 × 10⁻⁵) W

Power = (Energy/time)

Energy = Power × Time

Power = (3.929 × 10⁻⁵) W

Time = 1 minute = 1 × 60 = 60 s

Energy = (3.929 × 10⁻⁵ × 60)

Energy = 0.002357 J = (2.357 × 10⁻³) J

In Kilojoules,

Energy = (2.357 × 10⁻⁶) KJ

Hope this Helps!!!