Intensity Definition and 898 Threads

Homework Statement Two equal but oppositely charged points are 1.0 m apart in a vacuum. The electric field intensity at the midpoint between the charges is 2.4x10^5 N/C. What is the magnitude of each charge? Homework Equations Electric force= Kc (q/r^2) Kc=8.99x10^9 The Attempt at...

Hi! I am an English AS-level Physics student. I am stuck with my planning exercise and I thought these forums would be a good place to find some other people who are having similar problems, and perhaps we can work something out together. Homework Statement "You are required to design a...

Homework Statement A plane monochromatic light wave passes from a source inside an aquarium tank through water of index of refraction 1.33, then, at normal incidence, through a flat pane of glass of index 1.5 into air. Calculate the ratio of the intensity of the emergent light wave to that of...

This problem for some reason is giving me serious problem: A 1.00 kHz tone issued from a loudspeaker has an intensity of 100. dB at a distance of 2.50 meters. If the speaker is assumed to be a point source, how far from the speaker will the sound (a) have an intensity of 60.0 dB and (b) be...

Homework Statement Planning Exercise, Special Lamps may be purchased to help plants grow indoors. these lamps produce light with wave lengths comparable to natural sunlight. a manufacture wishes to check these lamps by measuring the output of the lamps at different wavelenghths. you...

In the single slit diffraction the condition for minimum intensity is that Del S= n*lamda n=1,2,3,...natural number the extreme path difference is equal to integral numbers of wavelength ( in the double slit experiment it is the condition for maximum intensity). It is understandable in the...

Homework Statement For my physics coursework, I have to design a laboratory experiment using an LDR to investigate how intensity of light emitted from a lamp varies with wavelength. In the procedure I will use diffraction gratings to separate light into wavelengths. The problem I am having is...

Homework Statement For my physics coursework, I have to design a laboratory experiment using an LDR to investigate how intensity of light emitted from a lamp varies with wavelength. In the procedure I will use diffraction gratings to separate light into wavelengths. The problem I am having is...

Homework Statement The EPM has finally crossed the fine line between party tricks and felonies with the genocide of the pigmy marmoset. You are now determined to make him ' pay the price. You fashion a makeshift sherical mirror/laster beam our of a roll of aluminum foil and a stick of...

Homework Statement Positive point charges q_1= 6.90 microC and q_2= 2.90 microC are moving relative to an observer at point P as shown in the figure. The distance from the observer to either charge is originally d = 0.190 m.The two charges are at the locations shown in the figure. Charge...

Homework Statement Some biologically active molecules rotate the direction of polarization of linearly polarized light, either clockwise or anticlockwise. For example, 5 gm of l-leucine dissolved in 100 mL of water causes a rotation by 0.550o while the same concentration of d-glutamic acid...

Homework Statement You need to design a diffraction grating that will disperse the visible spectrum (400-700nm) over 30.0 degree in first order. a) How many lines per millimeter does your grating need? b) What is the first-order diffraction angle of light from a sodium lamp (wavelength =...

Dear Friends, My longtime pending doubt here...! When we focus a mirror on the wall we get bright spot of the light. Ok. Now say, there is cube 6" x 6" x 6" whose inner walls are of mirror surfaces and opaque surfaces are the outer surfaces of the cube. In the center of the cube, in...

You are trying to overhear a juicy conversation, but from your distance of 25.0 m , it sounds like only an average whisper of 25.0 dB . So you decide to move closer to give the conversation a sound level of 80.0 dB instead. how close should you come? d= ...

The Problem : The sound wave with intensity 31 mW/m2 interferes constructively with a sound wave that has an intensity of 20 mW/m2. What is the intensity of the superposition of the two. I know that you can add the amplitudes for constructive interference or subtract for destructive...

Suppose you have a Cartesian coordinate system with: a 2uC charge at (0,0) and a -8uC charge at (4,0), why is there only one point in which the EFI is zero (-4,0)? Shouldn't that be the first point where the EFI is zero (so (-5,0),(-6,0)... all have Electric Fields of zero) The reason I...

If there are two bodies, such as a sphere and a thin rod (each with exactly the same charge), why does the sphere have a greater electric field intensity? Are there any other variables that influence the electric field intensity if the charge is not an ultimate dependent factor? If the...

Homework Statement 1) At a given point in space, the total light wave is composed of 3 phasors P1 = a, P2 = (a/2)e^(i(theta)), P3 = (a/2)e^(-i(theta)). What is the intensity of light at this point? Homework Equations The Attempt at a Solution I solved it in the following way...

Hi I have a question here from a chapter on sound. I'm not sure on how to solve this, so I was wondering if someone here could please give me a hand. Thank You! Question: A point source at A emits sound uniformly in all directions. At point B, the listener measures the sound intensity to...

Is there any relation to find it's strength? I have got some raw data - 1# it depends on distance of light source of the object 2# how big the luminous object really appears from that place 3# intensity of the luminous object 4# how opaque is the object whose shadow is being formed...

Homework Statement The howler monkey is the loudest land animal and can be heard up to a distance of 1.4 km. Assume the acoustic output of a howler to be uniform in all directions. The distance at which the intensity level of a howler's call is 49 dB, in SI units, is closest to: a...

A recording engineer works in a soundproofed room that is 36.2 dB quieter than the outside. If the sound intensity in the room is 2.45 x 10-10 W/m2, what is the intensity outside? It seems so ez yet I'm getting the wrong answer ok so here is what I am able to do the difference of 36.2dB...

What is the intensity of sound at the pain level of 120 dB? Compare this to that of a whisper at 20 dB? b=10 log (I/ I0) 120 dB=10 log (I/1) 10^12=(I/ 1) I= 10^12 W/m^2 b=10 log (I/I0) 20 dB=10 log (I/1) 10^2=(I/1) I=10^2 W/m^2 The intensity of 120 dB would be 10^12 W/m^2...

What is the intensity of sound at the pain level of 120 dB? Compare this to that of a whisper at 20 dB? I know this should be so simple, but it has me confused. I have the formula but I am just not sure how to apply it. I(db)=10 log _ 10 (I/I _ 0)

The velocity of sound in air of density rho=1.29 kg/m^3 may be taken to be 330m/s. Show that the acoustic pressure for the painfull sound of 10 W/m^2 ~ 6.5x10^-4 of an atm. (atm~10^5 N/m^2) What is acoustic pressure. This question is easy I am sure, but I don't really know what it is...

Why are pitch and frequency similar to loudness and intensity? I also have one more question! I have a test coming up on the properties of sound things likethe spped of sound etc? Does anyone have like an old test or something i can use to help study?

The problem is this: A firework charge is detonated many meters above the ground. At a distance of 400m from the explosion, the acoustic pressure reaches a maximum of 10.0 N/m2. Assume that the speed of sound is constant at 343 m/s throughout the atmosphere over the region considered, that...

Hi, This problem has me stumped and I keep thinking that I'm missing something simple. The question gives us a simple model for modelling a microwave. We consider a plane wave traveling through an object in the microwave (in the z direction), with no reflection. So, the general form should be...

http://x5.freeshare.us/view/?121fs535045.jpg In the above diagram, what does the % of transmittance means? I know the % of transmittance is the reverse of % absorption, but there are more C-H bond per molecule than C=O, why the intensity for C=O is higher(higher absorption)? I really have no...

i have to do a physics assignment and i got stuck at this quesion hope u guys can help. An interference pattern is formed on a screen by the superposition of two coherent light beams, one of which has four times the intensity of the other. What is ratio of maximum to minimum intensity in the...

From using a magnifying lens under the Sun, I gather it can focus all or most of the light impinging on its surface area to a small spot and that is how it is able to create a greater intensity light at its focus (disregarding absorption in the lens.) Correct? What portion of the total light...

hi all, may be my problem is a simple one. I want to calculate the intensity field resulted due to a UV lamp in side glss cylinder located at a distance from the lamp. The lamp is sorrunded 3 sides by reflectors such that 90% of the light power is reflected. now i have to calculate the...

Dear all, I have the next question: if we consider the classical definition of electromagnetic intensity it is given by [energy]/[time x surface^2]. At the same time intensity is related to the number of photons of the em radiation. So my question: given for example an intensity of 5W/[sec x...

I am having trouble with these two problems.. 1.By how many decibels do you reduce the sound intensity level due to a source of sound if you quadruple your distance from it? Assume that the waves expand spherically. For this one do I have to find ratios of I1/I2 and then substitute it in...

Does the luminous intensity due to an isotropic point source of light at a point on a surface depend on the angle it makes with the normal to the surface?

# The intensity of direct sunlight on a surface normal to the rays is Io. What is the intensity of direct sunlight on a surface whose normal makes an angle of 60 degrees with the rays of the sun? I think the answer is Io itself because for an isotropic point source of light the luminous...

the pain threshold of your ears is about 130 phon.The sound levelclose to a jet (r=1m) when it takes off is about 150 phon.How far do you have to go away in order to lower the intensity level below the pain threshold?? anyone pls tell me the formula to use so that i can calculate as i can't...

Hello all, I have a problem that requires some knowledge about Young's double slit experiment. The question is as follows: Imagine performing Young's experiment with one slit wider than the other so that the intensity passing the wider slit is four times as great as that passing the narrower...

Sir, 1) A thick plane mirror shows a number of images of the filament of an electronic bulb. It is said that of these images the first image is the brightest. Is it true? If so, is it because some energy is lost in traversing through the dense medium? 2) It is said that the...

We have been doing some experiments using a mercury light source and filters for each wavelenght and a Detector Box (phototube) to measure the output voltage, to investigate planks constant, stopping voltage, intensity's effect... the typical - "energy is quantised" idea. :zzz: There is one...

A person wears a hearing aid, which makes a sounds louder by 50 dB. This a) means the sound intensity is increased by 100,000 times. b) This also means that the amplitude of the soundwave is increased by ______ times? I know Intensity is portportinal to (Amplitude)^2... so does that mean I...

I'm attempting to calculate the above, but I'm stuck. What I have thus far: intensity is the time average of the poynting vector, where the poynting vector is the cross product of the E and B fields. Using the given expressions, I get: \frac{\sqrt{a^2 + b^2}}{\mu \omega} E_0^2 \exp(-2bz)...

I have a quick question about polarization. When I put a polarizer up an unpolarized source, say the polarizer blocks all the polarization in th y direction and so all the photons in the x direction comes out of the polarizer. Is the intesity halved? It seems to me that the intensity should...

i built a laser in my lab... it consists of one Ne-He tube with a concave mirror at one end and a window at the other end. i just put another mirror infront of tube's window to get the laser. i got one question i can't find an answer to, the lab's guide said the intensity of the laser depends...

Two Polaroid filters are initially crossed. The analyzer is rotated through an angle of 55.0 degrees. Find the fraction of the intensity incident on the polarizer which passes the analyzer. I used I1=1/2 Io I2= I1cos I2= 1/2 Io cos^2(theta) = 1/2 Io cos227.5° = .393 Io Is...

Hi! What can be said about the intensity ratios of characteristic X-rays (Kalpha to Kbeta ) originating from a X-ray tube? I mean roughly and in general, not for some very specific anode material. I first thought that K-L (Kalpha) transitions would be more likely to happen than K-M:s...

A research center measures sunlight intensity every hour every day. The measuring device stands on flat ground and therefore measures light accordingly. The output is W/m^2. The problem is that I need to utilize this value for a vertical window on a wall facing south. How can I best do this?

I am to use a pyranometer, a device that measures sunlight intensity. I am confused about the output unit it produces. It says on it's side 4.55 \cdot V/\left( {W \cdot m^{ - 2} } \right) but I'm not sure how to interpret this unit. All help will be appreciated...

Hi, if someone could help me figure this out I'd really appreciate it. Estimate the average power output of the Sun, given that about 1350 W/m^2 reaches the upper atmosphere of the Earth. I know the answer is 3.8 X 10^26 W but I don't know how to get there. I've tried different equations...

I need help with this problem... Suppose that the intensity of the sunlight that reaches Earth's upper atmosphere is approximately 1200 W/m2. Earth is about 1.5 times 108 km from the Sun. What is the total average power output of the Sun, assuming it to be an isotropic source?