# Is this question on Intensity of light from Sun correct?

• Jahnavi
In summary, the conversation discusses the intensity of light emitted from the Sun and whether the given values are accurate. The experts clarify that the given number is correct for the Earth's orbit, but it would be higher if you were closer to the Sun. They also mention the total power of the Sun and how it relates to the intensity at the Earth's surface. The conversation ends with the person thanking the experts for their clarification.

## The Attempt at a Solution

This is an example given in the book . But I am just wondering whether the question itself is correct .

How can intensity of light emitted from Sun is given a constant ? Shouldn't 1400 be the power emitted from Sun ?

If 1400 is power emitted from sun , then in part b) , n = 1400/E . We don't need radius of Earth to answer part b) .

This is different from what is done in the book .

Could the experts kindly let me know whether my objection is valid or not ?

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Jahnavi said:
How can intensity of light emitted from Sun is given a constant ?
It is given at the Earth's orbit. There it is a given number. If you were closer to the Sun, this number would be higher.

Jahnavi said:
Could the experts kindly let me know whether my objection is valid or not ?
It is not.

Jahnavi
Irradiance ## E=1400 \, watts/m^2 ##. The number is correct. That is the intensity (irradiance) at the Earth's surface. ## \\ ## Meanwhile the sun is about 865,000 miles in diameter and is 93,000,000 miles away. The total power ## P ## satisfies ## \frac{P}{4 \pi s^2} =E## where ## s=93,000,000 \, miles ## which is ## s=1.50 \cdot 10^{11} \, m ##.

Jahnavi
Thanks !

## 1. What is the intensity of light from the Sun?

The intensity of light from the Sun varies depending on factors such as the Earth's distance from the Sun and atmospheric conditions. On average, the intensity of sunlight at the Earth's surface is about 1,000 watts per square meter.

## 2. How is the intensity of light from the Sun measured?

The intensity of light from the Sun is measured using a device called a radiometer. This instrument measures the amount of light energy received per unit area over a certain period of time.

## 3. What affects the intensity of light from the Sun?

The intensity of light from the Sun is affected by several factors, including the Earth's distance from the Sun, the angle at which sunlight hits the Earth's surface, and atmospheric conditions such as clouds, pollution, and scattering.

## 4. How does the Sun's intensity of light impact our planet?

The intensity of light from the Sun is crucial for sustaining life on Earth. It provides energy for photosynthesis in plants, drives weather patterns, and regulates the Earth's climate. However, excessive exposure to the Sun's intense light can also have negative impacts, such as sunburns and skin cancer.

## 5. Can the intensity of light from the Sun change over time?

Yes, the intensity of light from the Sun can change over time. This can be due to natural variations in the Sun's output, such as sunspot activity, or human-caused changes, such as pollution and deforestation. These changes can have significant impacts on the Earth's climate and environment.