# Number of photons emitted from a light bulb entering the eye

• dymondahlis
In summary, the question asks how many photons enter the eye per second from a 100W bulb emitting light with a single wavelength of 6000*10^-10 m, given that the person is 1m away and the pupil diameter is 1mm. To solve this, the energy of each photon is calculated using E = hc/lambda, and then the proportion of light entering the eye is divided by this energy to find the number of photons. The proportion of light entering the eye is determined by the area of the pupil, which is a circle with an area of pi*r^2.
dymondahlis

## Homework Statement

A 100W bulb emits light of a single wavelength 6000*10^-10 m. If light spreads out uniformly in space, how many photons enter your eye per second if you are at a distance 1m from the bulb and the pupil diameter is about 1mm?

E = hc/lambda

## The Attempt at a Solution

I found the energy of each photon using E =hc/lambda and i know i have to divide the proportion of light entering the eye by this to find the number of photons entering the eye. I also know that the proportion of light entering the eye is area of pupil/ area of sphere. the area of sphere is 4*pi*r^2 = 4*pi*1 but what is the area of the pupil?

The pupil is a circle. What's the formula for area of a circle?

pi*r^2
i assumed it would've been harder to find.
thanks so much!

## 1. How many photons are emitted from a light bulb?

The number of photons emitted from a light bulb depends on the type and wattage of the bulb. On average, a 60-watt incandescent light bulb emits approximately 9 x 10^20 photons per second.

## 2. How many photons enter the eye from a light bulb?

The number of photons that enter the eye from a light bulb depends on the distance between the light source and the eye, as well as the angle of the light. On average, the human eye receives about 10^14 photons per second from a 60-watt light bulb held at arm's length.

## 3. How does the number of photons emitted from a light bulb affect vision?

The number of photons emitted from a light bulb can affect vision in terms of brightness and contrast. A higher number of photons can result in a brighter and clearer image, while a lower number may make it difficult to see or distinguish details.

## 4. Can the number of photons emitted from a light bulb damage the eye?

The number of photons emitted from a light bulb is not typically strong enough to cause damage to the eye. However, prolonged exposure to high levels of photons, such as from staring directly at the sun, can lead to temporary or permanent damage to the retina.

## 5. How can the number of photons emitted from a light bulb be measured?

The number of photons emitted from a light bulb can be measured using a photometer, which measures the intensity of light by detecting the number of photons that hit a specific area over a certain amount of time. Spectroscopy can also be used to measure the number of photons emitted at specific wavelengths of light.

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