Brightness Definition and 147 Threads

I have a question to ask everyone. Is there a positive correlation between the linear polarization degree of pulsars and their brightness in statistics? Or, is it true that the brighter the pulsar, the greater the linear polarization component?

a) sinθ = y / L where y = 1.26 m and L = 1.29m sinθ = 0.9767 β = (pi * a*sinθ) / λ where λ = 517.4 * 10^-9 m and a= 3.96 × 10^−6 m β = 0.000012151 / 517.4 * 10^-9 = 23.485 I / Io = (sin(23.485) / 23.485)^2 I / Io = 0.0002879 which is 0.2879 * 10^-3 b) asinθ=mλ where m =...

Derive formula for surface brightness The formula in question we wanna derive is: S(mag/arcsec^2) = M⊙ + 21.572 -2.5 log_{10} S(L⊙/pc^2). Best regards.

The answer key is (D) but I don't understand how to approach this question. I am guessing the wire is acting as short circuit path but how to know which bulb will be short - circuited? Thanks

Problem: Attempt at solution: So "energy passing through per unit area per unit time" is equal to $$I = \frac{E_i}{A t}$$ So for a the graph will be in the form of ##y=1/x##? For b) do we have to solve the differential equation $$dI = \frac{E_i}{A dt}$$?

What is the brightness of the sun compared to the sky that it lights up? I have a solar filter that only sees the sun. I just wonder if it is needed to be so dark that I can't see the sky anymore. I have plenty of camera options left to shorten exposure even with a filter a fraction as dense...

I was taking notes from a lecture on Quantum Physics and during the introduction, they gave an example of what led to the discovery of Quantum Physics: The electric bulb example where the brightness and colour of light depended on the temperature of the filament(see...

Hello, I built myself a spectroscope with a CD (where I removed the coating), similar to this one: With this I now want to look at light sources. However, some interesting lamps are a bit too bright to comfortably look directly into (through the spectroscope). Does anyone have an idea how to...

Assuming that the observer moves along the direction of the light, does the speed of the observer's measuring instrument relative to the light source (which may be close to the speed of light) affect the brightness and/or power flux density measured by the observer? I'm not sure about this...

How come when the illumination is from below, the central spot is bright, but when the illumination is from above, the central spot is dark?

Has any astronomer observed any seasonal changes in the brightness of stars lying close to the ecliptic plane? (Other stars are: d Cnc b=+0.08, mag.=+3.9; d Gem b=-0.18, mag.=+3.5; a Lib b=+0.33, mag.=+2.7.) Once a year these stars are occulted by the Sun. What happens from the date of...

I have a doubt regarding the role of the solid angle when calculating the power(W) with the brightness of the source I'm observing with area Asource. I was given the definition: with A the Aantenna. If now I take as an example the picture below to calculate W, we conisder as solid angle the one...

Cavities formed by red-hot coals appear brighter than the coals themselves. Is the temperature in such cavities appreciably higher than the surface temperature of an exposed glowing coal? At first i tried to interpret the "brightness" as a synonymum of intensity, anyway, a radiation emitted by...

Since the Earth orbits around the sun and very slightly changes its relative angle and position, does the brightness of a particular star change from season to the season?

The brightness of an LED is a result of the current passing through it. The current is a function of the voltage across the LED. The duty cycle represents the percentage of the time period that the signal is in the ON state ( which means that the voltage is at max value as compared to 0 V for...

I came across 2 similar example problems while studying for my exam and I want to make sure I get the differences between the two before I take my test later this evening. (This might be long but I have an exam coming up and I don't want to go into it with any uncertainties. I appreciate anyone...

Hello, I'm using photo-sensors from commercial and industrial cameras to document an experiment. Afterwarde I evaluate the change in brightness during the test of a fixed segment of every image I took. The ambient light condition is stable and the images are in raw files, but I'm unsure how raw...

Homework Statement Four identical light bulbs are connected to a battery as shown in the diagram. Switch S is originally closed. If switch S is opened, what happens to the brightness of each bulb? Homework Equations V=IR The Attempt at a Solution - By opening the switch, no more current...

Homework Statement A black and yellow body at room temperature are thrown into a furnace at very high temperature. How will the initial and final brightness of both compare? Homework Equations λT=constant The Attempt at a Solution The rise in the black body's temperature will be higher...

Homework Statement Homework EquationsThe Attempt at a Solution [/B] Sorry for the messy image . I have got the right answer by assuming certain values of the resistors . But I would like to know whether this question can be done logically without assigning numerical values to the resistors...

Hello, I am reading a review on weak gravitational lensing (https://arxiv.org/pdf/astro-ph/0509252.pdf) and they define the center of an image as follows: $$\vec \theta_c = \frac{\int d^2 \theta I(\vec \theta) q_I [I(\vec \theta)] \vec \theta}{\int d^2 \theta I(\theta) q_I[I(\vec \theta)]}$$...

Homework Statement Two 110-V light bulbs, one "25W" and the other "100W" are connected in series to a 110 V source. Then: a. the current in the 100W bulb is greater than in the 25W bulb b. the 25W bulb will be brighter c. the current in the 100W bulb is greater than that in the 25W bulb d. the...

Hello I'm working through a book (with answers) but am struggling with voltage, current, resistance and circuits. Please check my understanding below and let me know if I've finally understood. Thank you. In particular I'm confused in Q2 Q1. A student connects light bulbs, A and B, and...

The SMPTE 196M standard specifies screen brightness for cinemas, as 55 candela per square meter, open gate (no film in the projector, just white light). It used to be specified in terms of foot-lamberts, but let's stick to SI. I ultimately want to compare the brightness I see in a cinema, with...

I have some questions about projection lenses and screen brightness. Background I may be purchasing a BenQ PU9730 (http://www.benq.com.au/product/projector/pu9730/specifications/) for use in a large venue, projecting an image 3 x 5.3 metres. The projection booth is 18m from the screen (maximum...

Hi all, I don't know if I'm on the right forum to ask this, but maybe somebody knows anything about brightness temperatures measured by remote sensing devices. In a paper that I read "Atmospheric corrections for retrieving ground brightness temperature at commonly-used passive microwave...

Homework Statement In the circuit shown in the figure, what will happen to the brightness of bulb A and bulb B when the wiper moves from point X to point Y? Homework EquationsThe Attempt at a Solution [/B] When the wiper moves towards Y we get smaller resistance, hence the current intensity...

What is the Sun ray brightness quality after mirror reflection and what affects it? How to get the efficiency after reflection?

Homework Statement In the circuit shown, all the light bulbs are the same. Why is the following statement true? : A is the brightest. B and C are equally bright, but are dimmer than A. https://pbs.twimg.com/media/C6GllsQVMAA4chz.jpg:large...

I've read that L = 4 x Pi x b x d2 Where L = Luminosity (W) d = distance (m) b = brightness (W m-2) But in a real life applied situation, how does it work, how does one measure the distance and its brightness? And what does the 4Pi do?

Homework Statement The brightness of the bulb A in the following picture equals: A) half of the bulb B brightness B) equal to bulb B brightness C) Twice as bright as bulb B D) four times as bright as bulb B Homework Equations Ohms law Conservation of energy Faraday's law The Attempt at a...

Homework Statement Here is a picture of the problem https://www.dropbox.com/s/2bps6ga2o4hjpgw/hw4.png?dl=0 For those who don't want to click the link, basically the problem wants me to calculate the surface brightness of a flat surface at any angle if the source function S = B(T), which is a...

Homework Statement Homework Equations I know that power of a lightbulb/resister is I^2 * R The Attempt at a Solution OK. Here's my attempt: Let's consider the situation where we do not close the lightbulb and assume that the wires and switch are ideal because they have no resistance. I...

Homework Statement Homework Equations no equations The Attempt at a Solution I know that we will have an equal current flowing through bulbs 1 and 2 when we connect them in parallel in accordance with kirchhoffs voltage law which says that the voltage drops around both paths must be equal...

Homework Statement [/B] Given the circuit diagram (attached below), predict how unscrewing each bulb separately affects the brightness of the other two bulbs? Homework Equations N/A The Attempt at a Solution I predict that by unscrewing one of the bulbs, the other two will get brighter. This...

Homework Statement Which bulb(s) will have the higher light intensity?Homework Equations Resistors: Connection in series: same current Connection in parallel: same delta V The Attempt at a Solution A and C are in series. They'll be equally bright. B is not connected to the negative terminal of...

I have made a smartphone projector. But is has low brightness. How to increase brightness of projector... Help please

Homework Statement Two lightbulbs of resistance R1 and R2 (R2 > R1) are connected in series. Which is brighter? What if they are connected in parallel? Explain. Homework Equations P=V^2/R P=I^2R The Attempt at a Solution I know the solution. In series, P1=I^2R1 < P2=I^2R2, so R2 is...

Homework Statement A 60 W lightbulb and a 100 W lightbulb are placed one after another ( in series, the 60 W battery closer to the positive terminal of the battery) in a circuit. The battery's emf is large enough that both bulbs are glowing. Which is the true statement? A. The 60 W bulb is...

Hi my question is about how the brightness of stellar objects is effected when we look at them through a telescope. Firstly when I looked through a telescope I noticed there were more stars I could see. Is the reason because a telescope can gather more light than our eye or does it have...

Homework Statement Assuming that the average surface brightness within the effective radius is 19 mag/arcsec2, use the definition of the effective radius to estimate what the effective radius in kpc would be for NGC 4216 if it was an elliptical galaxy. Homework Equations All the logs are base...

Dear all, I am trying to understand the plot below: http://supernova.lbl.gov/PDFs/expansionhistoryphystoday.pdf by S.Perlmutter. However, I don't get the meaning of the "relative brightness" of SN. How is it calculated? Is the brightness of each SN compared to a special one?

Homework Statement All bulbs are identical, (no information given on resistance so assuming all the same) All the switches are closed and then S1 is opened, Does bulb 6 get brighter, dimmer or stay the same? Does bulb 4 get brighter, dimmer or stay the same? Explain briefly why. Homework...

Homework Statement [/B] Homework EquationsThe Attempt at a Solution I'm not really sure how to attempt this question tbh. In order for the lamps to have normal brightness I think the circuit must be parallel. I also think maybe for A there can only be one lamp per branch because there's...

I'm confused what the difference between the two are...I thought surface brightness was luminosity, but apparently it's not: L=Surface brightess x Area...But I came across a similar equation that seems to assume surface brightness is the same as apparent brightness. Please help! Edit: Also, why...

Homework Statement Bulbs in series are less bright than those in a parallel circuit. But are all the bulbs in the series circuit equally dim? Homework EquationsThe Attempt at a Solution I think for the purpose of high school physics bulbs in series are considered to be equally dim in a series...

AC is varying.So why does the brightness not vary?

From what I understand, in the equation P=\sigma AT^4, P is the power output of the star which is the energy radiated per second in EM radiation of all frequencies, and I think luminosity is also defined as the energy radiated per second in EM radiation of all frequencies. Therefore luminosity...

I'm trying to determine how bright my projection image will be on a projected surface. I'm struggling to find a formula for this. I'm using (for example) the Canon Rialis projector which is 4500 lumens. I would be using the zoom lens with maximum zoom so the throw ratio would be 7:1. At a...