# Questions tagged [intensity]

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### Does intensity of sound depend on temperature or humidity?

The intensity of sound $I$ can be written as $$I = 2 \rho v (af \pi)^2$$ I googled and found that increase or decrease of temperature doesn't have any impact on sound intensity. But why is that? ...
29 views

### Intensity of light and energy at a photonic level

If I understand correctly, the intensity of light is proportional to the number of photons hitting a certain area. If we then look at a single photon when described as a transverse wave, is its own ...
24 views

### Can we say that amplitude of light scattered by air molecules is inversely proportional to the square of wavelength of incident light?

As per Rayleigh's criteria of scattering of light by air molecules the intensity of scattered light is inversely proportional to the forth power of wavelength. AND WE ALSO SAY : Intensity of a wave ...
61 views

### What is $dE/dR$ and how does when $dE/dR=0$ makes electrical field intensity maximum? [closed]

Actually my question is that when $dE/dr=0$ then $dE$ also comes out to be zero then how does electric field intensity maximum when $dE/dr=0$. And also I don't understand that how does this value came ...
23 views

### Intensity of central maximum for a diffraction grating

If I send a typical 5 mW, 532 nm laser pointer beam through a diffraction grating (~1,000 slits/mm), then I'd expect the beam to cover something like ~1,000 slits. The resulting intensity of the ...
92 views

### Calculating measured intensity of a Gaussian beam

Consider a light source which emits a Gaussian beam with total power $P_0$, initial width $d$, and divergence half-angle $\theta$ (in radians). The beam radius, measured from the waist of the beam, ...
126 views

### Why doesn't the Intensity of laser light drop by $\frac{1}{r^{2}}$?

If we observe a laser we see its intensity wont drop by $\frac{1}{r^{2}}$ as seen for regular light sources as its very concentrated and even remain somewhat same for long distances (even though its ...
73 views

### Is the intensity of a light wave related to frequency of the wave?

My problem is: How can I resolve these following ideas? Energy of photons in an EM wave is proportional to the frequency of the wave Intensity of an EM wave is proportional to the energy that is ...
213 views

### Why sound gets weaker as it travels in air? [closed]

When we talk, our vibrating chords oscilate next air molecules which oscilate the next molecules and so on. Hence sound wave travels. As we know, energy that reaches the destination is not the same ...
324 views

### Would different sounds of the same intensity but different frequencies have the same harmful effect on the human ear?

The "safe noise exposure limits" I found on the internet only indicates the intensity of the sound in dB, but not the frequency. Does that mean that e.g. a 120dB sound with different ...
71 views

### Doubt in the definition of intensity

So I know that radiant intensity is defined as "power transferred per unit solid angle per unit area which is perpendicular to the direction of propagation of energy". So now I have a very ...
1 vote
89 views

### Why does an increase in my sound intensity lead to an increase in frequency range?

I am a biologist studying frogs, and as part of my research I use hundreds of thousands of audio recordings (.wav) from autonomous recording units. I use various software to create recognizers that ...
1 vote
111 views

### How to calculate the intensity of a light when using the ray model?

Suppose that there is a point light source with power $P$. We are interested in a single light ray visualised in the above picture. The ray travels a distance $r_1$ and encounters a surface. The ray ...
62 views

### What is the formula for the power of a laser at distance $x$ (taking attenutation into account)?

While this is inspired by science fiction, if I have a hypothetical laser weapon that needs to meet a very high energy requirement of energies of the order $1 \times 10^{22}$ Joules, what formula ...
42 views

1 vote
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### Deriving the Interference Intensity of Michelson interferometer

I am trying to equate the equation i found wikipedia: To the one given in my course notes which is: Assuming a 50/50 beam split i have 1/2 where i should not have one:
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### Question about unit for intensity

The picture is from one physics textbook about treating sun as a blackbody and compare the electromagnetic radiation spectrum. Note the unit used for Intensity in the picture shown, it's Watts / (...
19 views

### Why a wave whose intensity is modulated sinusoidally have different frequency compared to original wave even though intensity depends on amplitude?

While experimenting to find the velocity of light, instead of finding the velocity of light, we used the light wave whose intensity was varied sinusoidally and found the velocity of light using the ...
1 vote
84 views

### Derivation of the exoplanetary flux observed at Earth (solid angle problem)

I'm having issues understanding how Sara Seager, in her book "Exoplanet Atmospheres", determines the solid angle subjected to a detector on Earth. By the figure: The solid angle was defined ...
915 views

### Sound waves adding up [duplicate]

If there is a swarm of bees, why is it louder than a single bee? This question may sound stupid but ... if they are all buzzing at the same frequency with the same loudness and the phases of the sound ...
16 views

### If the range of a laser depends on its crossection perimeter does it mean that a wider beam would reach much longer distances?

If the range of a laser depends on its crossection perimeter does it mean that a wider beam would reach much longer distances? Let pressume that we can construct a 1m wide laser beam and as we know ...
31 views

### Acceleration due to incident radiation on plate

I have tried the following question and getting a wrong answer. Monochromatic light of intensity I falls over a blackened plate of area A, at an angle $\theta$ as shown in the figure. If 70% of light ...
775 views

### Convert $\rm Lux$ to $\rm W/m^2$

I use four LED matrix (UV, green, red, blue) to irradiate a solar panel with an area of S at a distance. The matrix is located at a distance l from the solar panel. I want to plot the volt-ampere ...
583 views

### What is the displacement amplitude of a 140 db sound wave?

I am teaching a unit on sound in my upper elementary science class, and my students are curious about how far air molecules are actually being displaced in a sound wave. I told them that if the air ...
63 views

### How was the black body intensity vs wavelength (or frequency) radiation curve historically produced?

I have read that Wilhelm Wien gave his formula to match the radiation curve of a black body as shown in the picture; which works well in high frequency region. Another formula by Rayleigh-Jeans is ...
262 views

### Does, and if so, why does the frequency of light and wavelength of light affect the photoelectric current?

It makes sense that intensity of light affects the photoelectric current, but what about the frequency and wavelength, given that intensity remains constant? The formula for intensity would be I = nhf/...
1 vote
122 views

### Why the intensity of a wave is $\Psi \Psi^*$?

In here at the bottom, it says the intensity of a wave is the wave phasor times it's conjucate $$I(x) = \Psi \Psi^* = |\Psi |^2$$ But when I compute the intensity of an electromagnetic wave in c.g.s, ...
23 views

### How does the spot size of light change the photocurrent?

I want to understand the photo electric effect. If I shine light at a surface then a photon can knock an electron off the surface if its energy $h\nu$ is larger than some minimum material specific ...
267 views

### I have seen people define frequency or amplitude in two ways, which one is correct?

I have a doubt on frequency and amplitude,I have seen people define these things in 2 ways,for instance, people define frequency in mainly 2 ways,if we draw a pressure-position graph of a sound wave,...
50 views

### Why solar flux concentrators can achive only $\rm 1500°C$ of temperature if Sun temperature is $\rm 5500°C$?

Why solar flux concentrators can achive only $\rm 1500°C$ of temperature if sun temperature is $\rm 5500°C$ ? If it is possible to concentrate a flux from a parabolic mirror of area $\rm 400\ m^2$ to ...
46 views

### Sound, additive principle or not? How to prove?

If we have $N$ sound sources with $L_1, L_2,...$ with intensities $I_1, I_2,...$. How to prove that $I_{total}= I_1 + I_2 + ...$ but $L_{total}$ is NOT $L_1 + L_2 + ...$
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### Is there a way to calculate the intensity of light absorbed that passed through a solid?

So I have lab I need to do for school and I need a formula that calculates the intensity of light transmitted through a solid (in my case sheets of paper). I had a probe that measured the intensity of ...
1 vote
139 views

### Law of amount of interference between different Sun rays that fall on a distinct point on Earth?

The double slit experiment shows that rays comming from different locations can cancel each other when touching a point on a screen if they are out of fase because of their wave properties. Is the ...
1 vote
88 views

### How does intensity depend on slit-width regarding Fraunhofer diffraction?

For a single slit, considered to be infinitely long, with size $b$ the intensity at any angle is given by: \begin{equation} I(\theta)=I(0) \bigg( \frac{\sin \beta}{\beta} \bigg)^2 \end{equation} ...
120 views

### Mathematical Derivation of Expression for the Total Power Received By Earth from Sun, via Integration [closed]

I recently tried to derive an expression for the total power received by the earth from the sun, using integration. However, I am stuck at an integration step. Would appreciate if anyone could help ...
1 vote
1k views

### Is the intensity of light dependent on number of photons per unit area?

I was learning about the photoelectric effect of light and there it says more the intensity of light, the more number of electrons will be ejected from the metal surface given that the frequency of ...
66 views

### How is energy in terms of Intensity and Amplitude comparable to Energy in terms of Frequency?

Let's take LASER light. It has a high energy ,in terms of Amplitude, let's take a red light, of same frequency ,we are giving each of these to two atoms , now atom no $1$ is subjected to LASER light ,...
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### Unequal arm length Michelson Interferometer Light Intensity

Imagine a Michelson interferometer with unequal arm length. A laser beam with an electric field of the form $$E(t,z) = 2E\cos(ωt+kz)$$ is incident on a 50/50 beam-splitter. The first arm is of length <...
1k views

### Inverse Square vs Exponential

I feel a little foolish asking this, but I keep reading sources which say that for an inverse square law relationship, e.g. light intensity vs distance from source, the intensity decays exponentially. ...
30 views

### Electron emission and photoelectric effect affected by intensity

It is said that when visible light is directed onto a metal surface, it doesn't emit electrons from the surface because intensity doesn't affect it. However, then it is said (relating to the equation) ...
Given a plane monochromatic electromagnetic wave propagating in $x$ direction, with associated electric and magnetic fields of the form: \$\overrightarrow{E}(x,t)=\overrightarrow{E_0}\cos(kx-\omega t), ...