# Will intensity of this light become infinity?

• P.Ramesh
In summary, the conversation discusses the intensity of light in a cube with mirrored inner walls and a lamp in the center. There are multiple reflections happening and the question is whether the intensity of light will be multiplied. However, it is believed that the intensity will remain the same as the light at the given distance. The discussion also considers factors such as reflectivity and the size of the light source.

#### P.Ramesh

Dear Friends,

My longtime pending doubt here...!

When we focus a mirror on the wall we get bright spot of the light. Ok.

Now say, there is cube 6" x 6" x 6" whose inner walls are of mirror surfaces and opaque surfaces are the outer surfaces of the cube. In the center of the cube, in the mid space, I install a lamp (say 100W electric bulb).

There are mutiple reflections happening since all the 6 walls are facing each other. Now If I introduce an instrument to measure the intensity or brightness of the light, How much it will be? 2 times, 3 times or 4 times or infinity?

But I feel the answer as the "intensity will be same as that of the light at the given distance". It won't get multipled. Still I want an detailed explanation with convincing reasons. Anybody to explain me please!?

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Let's say a mirror reflects x amount of light, x < 1. So we have for two opposite mirrors, for every hop,
1: 1(light from bulb)
2: 1(bulb) + x(light from hop 1 reflected by opposite mirror)
3: 1 + x(from hop 2) + x*x(from hop 1)
...
∞: 1 + x + x*x + x*x*x +... = 1/(1-x)
this is if I didn't missed anything. the rest of light, ∞ - 1/(1-x), will be consumed by mirrors and eventually melt them. unless they radiate the heat.

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whatta said:
Let's say a mirror reflects x amount of light, x < 1. So we have for two opposite mirrors, for every hop,
1: 1(light from bulb)
2: 1(bulb) + x(light from hop 1 reflected by opposite mirror)
3: 1 + x(from hop 2) + x*x(from hop 1)
...
∞: 1 + x + x*x + x*x*x +... = 1/(1-x)
this is if I didn't missed anything. the rest of light, ∞ - 1/(1-x), will be consumed by mirrors and eventually melt them. unless they radiate the heat.

Thanks for the reply. but it is not convincing because the brightness seems function of the wavelength... even i am also not sure.

i mean, x like integral flux reflected in all wavelengthes. oh well.

If you could get everything perfect (you can't), the intensity would continuously increase. Real mirrors have reflectivities under 100% and real lights are bigger than a single point and get hot.

## 1. What is meant by "intensity" of light?

The intensity of light refers to the amount of energy that is carried by a beam of light per unit area per unit time. It is measured in units of watts per meter squared (W/m²).

## 2. Can the intensity of light actually become infinity?

No, the intensity of light cannot become infinity. While it is possible for the intensity to increase to very high levels, it cannot reach infinity because there is a limit to the amount of energy that can be carried by a beam of light.

## 3. What factors affect the intensity of light?

The intensity of light can be affected by a number of factors including the source of the light, the distance from the source, and any obstacles that may block or reflect the light. Other factors such as the wavelength and polarization of the light can also impact its intensity.

## 4. How is the intensity of light measured?

The intensity of light is typically measured using a device called a radiometer, which can detect and measure the amount of light energy that is being transmitted. Some common units for measuring light intensity include lux, lumens, and candelas.

## 5. Why is it important to understand the intensity of light?

Understanding the intensity of light is important in many scientific fields, such as optics, astronomy, and photobiology. It can also have practical applications, such as in the design of lighting systems for buildings and in the development of technologies that use light, such as solar panels.