Radiation Pressure of 75 Watt Bulb at 8 cm

[FrankJ777]

b]1. Homework Statement [/b]
Estimate the radiation pressure due to a 75 Watt bulb at a distance of 8 cm from the center of the bulb.

Homework Equations

S=(E x B) , P = S/c

The Attempt at a Solution

I'm not sure were to start. How can I determine the value of E from a 75 Watt bulb.

 

[mgb_phys]

You need to know how the momentum and energy of a photon are related to its wavelength.

 

[thomate1]

I would approach this problem by first understanding what is meant by "radiation pressure" and how it is related to the concept of electromagnetic radiation. Radiation pressure is the force per unit area exerted by electromagnetic radiation on a surface. It is caused by the momentum transfer of photons, which are the particles that make up electromagnetic radiation.

To estimate the radiation pressure of a 75 Watt bulb at a distance of 8 cm, we first need to determine the intensity of the radiation emitted by the bulb at that distance. Intensity is a measure of the power (in Watts) per unit area (in square meters). We can use the inverse square law, which states that the intensity of radiation decreases with the square of the distance from the source, to calculate the intensity at 8 cm.

Using the given power of 75 Watts and the distance of 8 cm (or 0.08 m), we can calculate the intensity using the following equation:

I = P/(4πr^2)

Where I is the intensity, P is the power, and r is the distance from the source.

Plugging in the values, we get:

I = 75/(4π(0.08)^2) = 2,346.21 W/m^2

Next, we need to calculate the energy flux density, which represents the amount of energy per unit time and unit area. This is given by the equation:

S = cI

Where S is the energy flux density and c is the speed of light.

Plugging in the values, we get:

S = 3 x 10^8 m/s x 2,346.21 W/m^2 = 7.04 x 10^11 W/m^2

Finally, we can use the equation P = S/c to calculate the radiation pressure, where P is the radiation pressure, S is the energy flux density, and c is the speed of light. Plugging in the values, we get:

P = 7.04 x 10^11 W/m^2 / 3 x 10^8 m/s = 2.35 x 10^3 Pa (or 2.35 x 10^-2 N/m^2)

Therefore, the estimated radiation pressure of a 75 Watt bulb at a distance of 8 cm is approximately 2.35 x 10^-2 N/m^2. It is important to note that this