# How do you calculate relative light intensity?

Inverse square law The light energy at three times the distance away (3d) is spread over nine times the area. So, the light intensity is inversely proportional to the square of the distance – this is the inverse square law. For each distance of the plant from the lamp, light intensity will be proportional to 1 d 2 .

## What is Malus law formula?

We know, an unpolarized light passes through a polaroid its intensity becomes half of its initial intensity. If it passes again through any other polaroids, then its intensity given by Malus law is, I = I 2 cos 2 θ

## What is the intensity of the light in W m2 after it passes through the first polarizer?

[5 points] (a) Unpolarized light, with an intensity of 1000 W/m2 is incident on the first polarizer. What is the intensity of the light transmitted by the first polarizer? When unpolarized light passes through a polarizer, the intensity is cut in half. Therefore, the transmitted intensity is 500 W / m2.

## How do you find the intensity of light transmission?

When polarized light of intensity I0 is incident on a polarizer, the transmitted intensity is given by I = I0cos2θ, where θ is the angle between the polarization direction of the incident light and the axis of the filter. The transmitted light is polarized along the axis of the polarizer.

## How do you calculate light intensity given power and distance?

The intensity of light is inversely proportional to the square of the distance. This means that as the distance from a light source increases, the intensity of light is equal to a value multiplied by 1/d2,.

## What is the formula for light energy?

The energy of a single photon is: hν or = (h/2π)ω where h is Planck’s constant: 6.626 x 10-34 Joule-sec. One photon of visible light contains about 10-19 Joules (not much!) the number of photons per second in a beam.

## What is Brewster law?

Brewster’s law, relationship for light waves stating that the maximum polarization (vibration in one plane only) of a ray of light may be achieved by letting the ray fall on a surface of a transparent medium in such a way that the refracted ray makes an angle of 90° with the reflected ray.

## What does Snell’s law state?

The Snell’s law of refraction states that: The incident ray, the refracted ray and the normal at the point of incidence, all lie in the same plane. The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for the pair of the given media.

## Which method of polarization is used in Malus law?

where I0 , is the intensity of the light before the polarizer. Equation 1 is the so called Malus’ law, named after the French physicist Étienne-Louis Malus, who discovered optical polarization in 1808. In this experiment, a source of polarized light, a polarizer, a photometer and a way to measure angles are needed.

## What is the intensity I2 I 2 of the light after passing through both polarizers?

After passing through both polarizers the intensity is I2=140W/m2 I 2 = 140 W / m 2 .

## What is the intensity in W m2 of the light emerging from the second polarizer?

What is the intensity of the light emerging from the second polarizer now? Going through each polarizer the intensity is reduced by a factor of 3/4. After emerging from the first polarizer the intensity is 16 * 3/4 = 12 W/m2, and is reduced to 12 * 3/4 = 9 W/m2 after going through the second.

## What is the intensity of the light once it has passed through the polarizer?

The intensity of the unpolarized light decreases. Explanation: The intensity of the unpolarized light when passed through a polarizer is reduced by a factor of ½. where I0 is the initial intensity and θi is the angle between the light’s initial polarization direction and the axis of the polarizer.

## What is K in intensity of light?

In the Young’s double – slit experiment, the intensity of light at a point on the screen where the path difference is λ is K,(λ being the wave length of light used).

## How is led intensity calculated?

For a red LED (660 nm) with Ie = 0.1 mW/sr, the luminous intensity is calculated as below: Iv = Ie*Km*V(l) = 0.1 mW/sr*683 lm/W*0.061 = 4.2 mcd. For high intensity devices like TELUX, the characterization is carried out by a measurement of luminous flux, wavelength and forward voltage.

## What is intensity of light in physics?

The term intensity is used to describe the rate at which light spreads over a surface of a given area some distance from a source. The intensity varies with the distance from the source and the power of the source.

## Does light intensity change with distance?

There is an inverse relationship between distance and light intensity – as the distance increases, light intensity decreases. This is because as the distance away from a light source increases, photons of light become spread over a wider area.

## What is the relationship between power and intensity?

Intensity is defined to be the power per unit area: I=PA I = P A and has units ofW/m2.

## How do you calculate amplitude and intensity?

As defined in physics, the intensity of a wave is proportional to the square of its amplitude (A2 ∝ I).

## What is the speed of light 3×10 8?

The speed of light in vacuum is 3×108 m/s. Sunlight takes about 8 minutes to reach the Earth.

## What is Brewster law and proof?

Brewster’s law is a relationship of light waves at the maximum polarization angle of light. This law is named after Sir David Brewster, a Scottish physicist, who proposed the law in the year 1811. The law states that the p-polarized rays vanish completely on different glasses at a particular angle.

## What is Brewster law and derive formula?

So, cosθBsinθB=tanθB=μ1μ2. θB=tan−1(μ1μ2) The reflected rays of unpolarized light incident at θB are perfectly polarized in plane perpendicular to the incidence plane (and transmitted plane). There is no reflection for p polarized light incident at θB.

## What is angle of polarization and state Brewster’s law?

Brewster’s law states the tangent of angle of polarization is equal to the refractive index of the medium. Mathematically n=tanip.

## What are the 3 laws of refraction?

• The incident ray, the refracted ray, and the normal at the point of incidence, all lie in the same plane.
• The ratio of the sine of the angle of incidence ‘i’ to the sine of the angle of refraction ‘r’ is constant for the pair of given media is always constant.

## Why sin is used in Snell’s law?

It is just a convention to choose the angle between the normal to the interface and the ray of light, which makes the sine function appear.