The human eye can respond to as little as 10^-18j of light energy. for a wavelength at the peak of visual sensitivity, 550 nm, how many photons lead to an observable flash?

Approximately 3 photons

Explanation:

The energy of a photon at the peak of visual sensitivity is given by:

where

h is the Planck constant

c is the speed of light

is the wavelength of the photon

Substituting into the formula,

This is the energy of one photon. The human eye can detect an amount of energy of

So the amount of photons contained in this energy is

so approximately 3 photons.

find the surface area of the sphere to the nearest square unit. use a calculator.

a. 254 in.2

b. 64 in.2

c. 127 in.2

d. 1,018 in.2