Intensity Definition and 966 Threads

For a star.. Apparent Magnitude = -2.5log10 I K And I = I0/d^2 So in terms of I0... Apparent Magnitude = -2.5log10 (I0/d^2) And the Stefan-Boltzmann law says: Energy Flux = Sigma(T^4) In my reading it says that Intensity is the energy emitted per unit of area per unit of time. It says the same...

To begin with, I am trying to understand how does ##E^2 (x,t)## transform to ##A_y^2 + A_z^2##. And, noting that the already established equation of ##E^2 = E_y^2 + E_z^2##, I would assume that ##E^2 (x,t)## somehow ends up to being ##A_y^2 + A_z^2##. However, noting that ##E^2 = (A_y...

I was looking up the maximal amount of noise allowed by current laws, that one can produce. I found that in my region one can produce sounds of up to 45 dB in the period from 22 pm to 7 am. But, it seems evident that the decibels fall off as we distance ourselves from the source. So shouldn't...

Hi, Would it be correct to say that at Brewster's angle, all the incident light which has its electric field parallel to the plane of incidence gets refracted, and the rest of light whose electric field is perpendicular to the plane of incidence gets reflected? For example, if the light whose...

I'm still on part a. I think that i may have the wrong equation for intensity. I'm not sure I'm using the right numbers for the "first minimum". I started with getting the wavelength λ=(ax)/D since the first minimum occurs at m = 0.5 I multiplied the distance to the first minimum by 2 to get...

Is the intensity of a general electromagnetic wave always the norm of its Poyinting vector? Or are there other notions of intensity?

The equation above (from Wikipedia), assumed that the Gaussain beam has polarization in x-direction, as I know that the polarization means that the oscillation direction of the electric field and so the intenisty... so how we get circular intensity in every direction which means in x and y...

Looked upon this and can't seem to find anything. The formula I=Icos^2theta seems to only work for polarization filters, which is not this case. On the other hand, the brewster's angle only c.aclates the angle when the REFLECTED light is polarized, not the REFRACTED light. Hence I am confused...

Hi all, just wanted to check into check on my workings if it is correct :) So if index of lens is more than film, both rays will have phase change, and hence for constructive interference: ##2nt=m\lambda ## where n =1 and thickness = 100nm When m=1 , wavelength is 200nm m =2 wavelength is...

I think that what happens is that the amplitude becomes sqrt(2)/2A in the slit filtered, as opposed to A in the other slit. I suppose we will still get constructive interference from the slits, so the value (1+sqrt(2)/2)A will be reached as opposed to 2A in the usual experiment. However, the...

The parabolic mirror pictured below is such that all incident rays, neglecting diffraction, are reflected towards a focus. A question states that the light cannot be focused to a point precisely, since there exists a circular diffraction pattern in the focal plane. The following diagram is...

I've been giving this some thought. It's clear that the stiffners will increase the resistance of the material so that the energy release is no longer high enough to cause further fracture. I'm just not sure what formula I can use to take into account the new resistance. I suspect part 1 of the...

Inner conductor radius = 1cm outer conductor radius = 10cm region between conductors has conductivity = 0 & 𝜇r = 100 𝜇r = 1 for inner and outer conductor Io = 1A(-az) 𝑱(𝑟) = (10^4)(𝑒^-(r/a)^2)(az) Problem has cylindrical symmetry, use cylindrical coordinate system. Find the total current...

Hello! I am a bit confused by the formula for light intensity in the case of interference. In the books and online resources that I read, this is given as: $$I = I_0 \cos^2(\frac{\pi d \sin \theta}{\lambda})$$ where ##d## is the distance between the slits, ##\lambda## is the wavelength of the...

Two similar speakers are connected to a stereo system that emits a signal of frequency 𝑓. However, the signal to speaker B is inverted so that positive voltage becomes negative (but with the same absolute value) and vice versa for negative voltages that become positive. A sound intensity meter...

I'm not sure! I'm really lost on this problem to be honest.

For t < 0 , all I can think of is a qualatative " the field is zero because the intensitity is 0 when the burst of light hasn't been emitted yet " For t >= 0 , I've tried squaring the given E and that let's me say the amplitudes are proportional (with a cos^2 term in the mix) But I feel like...

Given that L is the luminosity of a single star and there are n stars evenly distributed throughout this thin spherical shell of radius r with thickness dr, what is the total intensity from this shell of stars? My calculations were as follows: Intensity is the power per unit area per steradian...

Homework Statement: In a double slit experiment let d=5.00 D=30.0λ. Estimate the ratio of the intensity of the third order maximum with that of the zero-order maximum. Homework Equations: interference diffraction i guess the goal is this equation ##I_{(\theta)}=I_0 \times(cos^2\beta)\times...

Hello, I have an ordinary light (not laser) collimated to produce a parallel beam. After traveling a distance in air, the beam has diverged significantly. The intensity decreases as the radial distance increases. Now I need to estimate the intensity profile along all radial distances inside the...

We can solve for the maximum 5 lux illumination distance with the above equation. E = 10.76*(35,000/d^2) d = 275 feet (approximately). However, the 5 lux illumination distance is not 275 feet. The 35,000 cd value is not an axial intensity value. It is at a point that is slightly down and to...

I = I0[ sin (φ/2)/(φ/2)]2 Given such equation I don't understand why in sin(φ/2) are used degrees and in (φ/2) at the denominator radians. If there is any reason for it i forgot about it 😓. Is there anyone so kind to explain to me why is like that? Thanks in advance

Diagram Calculations as follows $$\frac{I_{total \: Reflection}}{I_{Incident}}=\frac{I_{R_1}+I_{R_2}}{I_0}*100=\frac{R*I_0+(R*T)*I_0}{I_0}$$ Subbing in the relevant equations given in the question $$\frac{I_{total \...

I is proportionate to E. r = 4.3xxm So I put 0.75I The answer is 49mW.. But I got 97.xxmW What is wrong?

https://pmt.physicsandmathstutor.com/download/Physics/A-level/Past-Papers/AQA-Old/Unit-5/June%202016%20MS%20-%20Unit%205-2A%20AQA%20Physics%20A-level.pdf One question on this the mark scheme seems to skip this step as the intensity is Power per unit area , when you make I sun = I quaser *...

I have obtained seeds of a rare rhododendron species. These seeds are contaminated (experimentally determined). While I have tried several common methods, none decontaminated the seeds. Lately, I have read that so many joules of UV light at approximately 254nm will prevent replication and...

as intensity is power per unit area and as power is proportional to energy, then increasing intensity increases energy of the photons?no? So if energy increases so will the speed of the electrons more energy to the kinetic energy after work function? the answer is current

area of a sphere 2.0 m radius: idk what to do after this point I am lost help answer is 3.16*10^9

First, I calculated the power generated by the solar panel in one day. So since the intensity is 1.0e3 watts per 1 m2. 10% of this peak power is utilized so (1000)(0.10)=P-utilized=100W (per 1 m2) the solar panel has the efficiency of 13% so of this power only 13% is useful. P-useful=...

Since light intensity is proportional to the amplitude of the EM wave, and wave amplitudes undulate up and down, does this result in natural intensity flickering of observed light? For visible light, the frequency is extremely high, but it might be more easily observable in ELF waves.

Homework Statement A thin (460 nm) film of kerosene (n=1,20) is spread out on water (n = 1,30). Light hits the (horizontal) surface of the film coming (almost) perpendicularly from above. A diver underwater, below the film. a) Find out the visible wavelength reflected into air that has the...

https://www.nature.com/articles/s41561-018-0288-0 (article is behind a paywall). Popular Science version: https://motherboard.vice.com/en_us/article/9kpywp/Earth's-magnetic-field-collapse-ediacaran-core-solidification Using samples of rock from the Ediacarian period, 565 million years ago, it...

Hi all, I would like to calculate light intensity of a bulb from 0.5 meter. Which formula shoul i use? I have a PV. Dimensions are 12x12 cm. Bulb is 100 Watt. Thanks

Why is solar spectral intensity per wavelength different than solar spectral intensity per frequency?

The Attempt at a Solution The solution I keep coming up with is (G) , but the solution sheet says it is (C). I assumed it was (G) because since the slit width is halved the central maximum is bigger so I assumed that X would now be part of the central maximum. Therefore the intensity would be I_0.

Homework Statement Homework Equations (1) Φ = 2π*(dsinθ/λ) (2) Itotal = I0 cos2(Φ/2) (3) Itotal = I0 cos2(πdy/λR) λ = 585 * 10-9 m R = 0.700 m d = 0.320 * 10-3 m y = ? The Attempt at a Solution a) I used eqn (1) and divided the total oscillations by a complete oscillation to find the...

Hello Forum, A sound wave intensity (pure frequency) is proportional to the square of the wave pressure amplitude, i.e. ##I \approx p_0^2##, where ##p_0## is the pressure wave amplitude: ##p_0 sin(\omega t \pm kx)##. This means that the (gauge) pressure value goes larger (positive) and lower...

Homework Statement If X represents the intensity of monochromatic blue light and Y represents the energy of each photon of the light, which one is the correct graph below? Homework Equations KE=hƒ-∅, where ∅ is the work function Energy of a photon= hƒ The Attempt at a Solution Increasing the...

Consider the traditional thought experiment of moving train observers, the "stationary" observers, and the flash of a lightning strike at the midpoint of the train. It seems that the stationary observers would expect the train observers to see different flash intensities (due to different...

Homework Statement If the frequency and intensity of a light source are both doubled, show that the saturation photo-current remains almost the same. 2. Relevant Graph https://cnx.org/resources/e73bf218926bd39de4a52bafe3a82d04bbf73542/CNX_UPhysics_39_02_photoexp1.jpg The Attempt at a Solution...

I have two lasers with different intensity distributions (shown below) — one is Gaussian and the other one is rectangular (having the shape of a Fresnel diffraction pattern at the target). I am trying to compare the efficacy of the two lasers for burning a certain material (I am really...

754/5000 I am using the fluroescence spectroscopy technique to obtain the fluorescence spectrum of exposed neuroblasts to uv radiation (355 nm) from a Nd:YAG source and I need to characterize the radiation pulses of the laser. Specifically, I use a spectrometer (Avantes brand) with integration...

Homework Statement Homework EquationsThe 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...

Hello Everybody, I'm having issues defining a set of equations that calculates the Temperature of a black body object when provided with one of the following: Radiant Intensity [W sr-1] Spectral Intensity [W sr-1 m-1] Radiance [W sr-1 m-2] Spectral Radiance [W sr-1 m-3] Irradiance Flux...

I am trying to evaluate SIF for 3D plate using ansys APDL. Please share tutorial/notes if available.

I measure sound (dB) from a speaker at 0cm and 100cm using a diaphragm microphone. 0cm-100dB, 100cm-30dB diaphragm microphone cinsists of a diaphram, coil and a permanent magnet. the coil is attached to the diaphragm, when a sound wave hits the diaphragm it causes to move back and forth which...

Homework Statement Let a charge oscillate on a straight line between -a to +a with a frequency ω and according to the law: κ (x.t) = κ° sin(πx/a) e^(-iωt) I have to find the following: 1. Vector potential in the dipole approximation 2. Integral of the intensity of radiation Homework...

If diffraction angle 2θ represents Miller indices, what does intensity represent particularly in the context of quantitative XRD?

Homework Statement Find the sound intensity of a thunderbolt 1 km away. What sound intensity (dB) is it 1 km away? The thunderbolt can be heard up to 20 km away. The sound is spherical. The air absorbs nothing. Homework Equations L = 10 \cdot lg(\frac{I_1}{I_0}) \Delta L = 10 \cdot...

Homework Statement Approximately 4% of the intensity of light is reflected at a glass-air boundary. Classically one expects roughly 8% of light to be reflected from a thin glass plate (4% at the front and back boundary). Outline briefly what quantum theory predicts for a single photon instead of...