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53 views

Decrease in temperature due to radiation

Can radiation cause the temperature to decrease? Because, in my Physics textbook, it is written that: ln winter nights, the atmospheric temperature goes down. The surfaces of windowpanes, flowers,...
0
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2answers
71 views

Why is sunscreen more important in the middle of the day?

I suppose that if the Earth had no atmosphere and no magnetosphere, then when standing up on the surface of the Earth -- say, on the equator -- my body would catch more radiation from the sun in the ...
0
votes
0answers
213 views

What are the average wavelengths and brightnesses of sunlight across the stages of twilight?

I understand that before sunrise, twilight shows several colors, so I'm looking for the average color (wavelength) and brightness (lux) of light that is being projected from the sky before the sun ...
1
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0answers
47 views

Why is the color of aurora borealis the way it is?

Why is aurora borealis mostly green, instead of pink, even though green light is emitted by excited oxygen atoms and pink light by excited nitrogen atoms? As nitrogen is present almost more than ...
20
votes
2answers
5k views

What is the scientific explanation for radio waves bending around the Earth?

The experiment This experiment is documented in a documentary called Convex Earth. The exact location the following information is taken from starts at 14:25. High frequency directional antennas are ...
4
votes
1answer
806 views

Why microwaves used in satellite communications?

I've been reading recently that:- EM waves with a shorter wavelength have shorter range in air/other medium Microwaves are used in satellite communications over radio waves. This doesn't make sense ...
1
vote
1answer
46 views

Plausible/ creative assumptions for solving equation of radiation transfer

I'm currently looking at the equation of radiation transfer given by $$\frac{1}{c}\frac{\partial }{\partial t}I_{\gamma} + \hat{\Omega} \cdot \nabla I_{\gamma} + \left ( k_{\gamma, s} + k_{\gamma, a}...
1
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2answers
120 views

Communications: Ground wave Propagation

(I wasn't having any tag for this question(Example: Communication-Systems, Modern-physics.)) I was studying ground wave propagation, my book writes the lines about it without explaining it. I really ...
1
vote
3answers
117 views

L-band for search radars?

I'm making my way through the Linesman-related section's of Gough's Watching the Skies. Linesman was developed to counter the carcinotron jammer. The main solution was the Type 85, which had 12 ...
0
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3answers
948 views

Why do we feel the sunlight the second the sun gets out of the clouds?

The earth is 149.600.000 km away from the sun and the speed of light is 299 792.458 kilometres / second, therefore, it would take sunlight, on average, 8 minutes and 20 seconds to reach earth. Now, ...
2
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0answers
35 views

What is the current limiting factor for GPS clock synchronization precision?

In the (slightly dated) paper 'Quantum Clock Synchronization Based on Shared Prior Entanglement' [R. Jozsa et al., Phys. Rev. Lett. 85, 2010 (2000)], the authors describe the GPS synchronization ...
2
votes
1answer
1k views

Why does the sun/moon appear red when there are fires?

Recently, in the United States, the moon and sun have become very deep red when they are near the horizon. The reason given for this is that there have been extensive wild fires in the Northwest. So, ...
0
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2answers
147 views

Mobile phone wavebands and signal attenuation

We know low freqs. (800 Mhz) are preferred for rural area for they are travelling great distances. So, why do em waves (of mobile phones) with lower frequencies travel greater distances than em waves ...
3
votes
1answer
327 views

Does aerosol particulate matter attenuate UVA more as compared to UVB?

I am trying to understand if winter aerosol particulate matter has a greater impact on UVB radiation as compared to UVA radiation. Would the attenuation be mainly due to scattering? I am asking this ...
3
votes
1answer
698 views

What is meant by the “cosine corrected response” of a pyranometer?

I have done an experiment that involved placing a pyranometer on a flat area and measuring the solar irradiance. The pyranometer used was a Kipp & Zonen CMP3 The irradiance1 is proportional to $\...
2
votes
2answers
623 views

Similarities between light and other frequencies of EM waves

This may be a ridiculous question, but I'll learn something from it! Let's say there's a TV transmitter transmitting at 100kW. I can receive the station just fine 20 miles away. The antenna is 300m ...
0
votes
1answer
317 views

Measuring the irradiance due to solar radiation with a pyranometer

Background information I carried out an experiment where a pyranometer (on a flat surface) was used to measure the irradiance at the ground due to solar radiation over a range of solar zenith angles (...
5
votes
1answer
359 views

How to correctly calculate the colour of the sky?

It is well-known that the sky is blue due to Rayleigh-scattering. What bothers me though is the question how to actually calculate the spectrum of the scattered sunlight. Yes, use one of the formulas ...
2
votes
1answer
5k views

What would the sky look like if the Sun was a different type of star?

Barring, of course, all other issues that wold naturally arise from the following question - if we made the sun a cooler, red star or a hotter, blue star, what impact would that have on the colour of ...
4
votes
4answers
22k views

How much lux does the Sun emit?

I want to know how much lux the sun emits on a bright day - I don't mean when one stares directly at the sun, but rather when one walks casually outside when the sun is shinning brightly. Now the ...
0
votes
1answer
94 views

What would happen to the Earth's atmosphere if all the solar radiation was in the extreme ultraviolet?

According to this, our Earth's atmosphere is completely opaque to radiation with wavelengths less than 100 nm as this radiation has enough energy to ionize the air. Since the surface temperature of ...
3
votes
2answers
6k views

Can someone explain to me the concept of atmosphere opacity?

On this diagram, why is the atmospheric opacity shaped as it is? If we are able to see lights due to low atmospheric opacity, why can't we see radio waves, when the atmospheric opacity is so low for ...
4
votes
1answer
2k views

Can atmospheric pressure literally push electromagnetic waves?

I work for an IT company and some time ago we had an issue with our wireless internet. We are 5 miles away from the ISP's antenna. Our Sys Admin expressed the view that the electromagnetic waves are ...
2
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2answers
679 views

Does gravity affect radiation incident on the planet?

Just curious ... Known facts: When outside the atmosphere levels of radiation are higher Typically such radiation is CBR, Solar Radiation Question: If the matter of the atmosphere and ...
1
vote
1answer
80 views

Weather Radar Interpretation - Radial Rays

I was browsing the NEXRAD radar feeds (I'm not an expert, just figuring them out) and I came across the following signature (visit the link to view the radar image) http://cl.ly/3n0y0p0g2M0K2B313g3U ...
3
votes
2answers
3k views

Why is the atmosphere transparent in the visible spectrum?

One of the great 'coincidences' in physics is that the Sun happens to shine most brightly at exactly the wavelengths our eyes can see; it's an easy explanation that our eyes evolved to make the most ...
2
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4answers
1k views

Electromagnetic wave reflection vs. light reflection

Related: x-ray interaction with atmosphere I know that electromagnetic waves of particular frequencies reflect from the ionosphere. And the light (which from one perspective is an electromagnetic ...
3
votes
3answers
5k views

x-ray interaction with atmosphere

Why x-ray are stopped by atmosphere while they are more energetic than UV or IR? They certainly interact with atmosphere but I can't understand which phenomenon stop them.
1
vote
1answer
187 views

range of infrared light

I notice in the EMS chart that only half of the IR range will travel through the earth's atmosphere. So in the range of frequencies that penetrate the atmosphere what frequency travels farthest?