Intensity Definition and 966 Threads

1. Homework Statement : Consider two lasers, one blue and one red. Which of the two lasers has the higher intensity? 2. these are my choices: The blue one. Cannot be decided based on the information given. The red one. 3. The Attempt at a Solution : The difference between these...

Homework Statement A point source of sound emits energy equally in all directions at a constant rate and a person 8m from the source listens. After a while, the intensity of the source is halved. If the person wishes the sound to be seem as loud as before, how far should he be now...

Homework Statement A small source of sound radiates energy equally in all directions. At a particular frequency, the intensity of the sound 1.0 m from the source is 1.0 x 10-5m Wm-2, corresponding to an amplitude of oscillation of air molecules of 70milimetre. (Assume no energy loss) Find...

I would like to calculate the intensities of Hydrogen spectral lines for the case of Hydrogene at temperature T contained inside a volume V. I reckon that what I need is 1)The mean population of the upper energy level 2)The probability of transition between the levels I believe that...

What causes the feedback (a noise increasing in intensity and pitch) sometimes heard when people speak through microphones? I'm sure I have enough background to understand an explanation, I've just never thought about it before.

Homework Statement A person is a certain distance away from a plane with three equally noisy engines at 120 dB. What is the sound intensity if two of the engines are shut off? Homework Equations B (in dB) = log I/Io The Attempt at a Solution using this equation: 120 dB = 10 log...

Intensity of light constant..why rate of emission of electrons changes?? Intensity of light constant..why rate of emission of electrons changes as frequency of the incident light increased??... is the rate increase or decrease?? help me.. thanks..

Please check to see if my solution is correct: Question: If a light source were increased by a factor of 2 in intensity, what would happen to the value of KE_max of each photoelectron? My solution: KE_max would stay the same because increasing the intesity by a factor of two would only...

Intensity of Light-- What factors contribute? What factors affect the intensity of light? What is intensity? Are the relationships or equations that link the intensity of light to other variables? I'm asking this because I'm not quite understanding intensity vs. frequency. I'm studying the...

Hi folks. I have read in several papers that the electric field intensity adjacent to the very tip of an electrode (the "point" in a point-plane geometry) surrounded by a dielectric medium is given by 2V / [r ln(4d/r)] where r is the tip radius, d is the point-plane spacing, and V is...

Hey! Im quite confused about spherical waves. I mean, I understand that a spherical wave can be described by \Psi = \frac{1}{r} e^{i r}, because the intensity of such a wave decreases as 1/r^2. The intensity of such a wave is given by I = 1/r^2 which makes sense to me. But a...

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 Derive the equation describing the Fraunhofer intensity pattern from a single slit of width b centered at the origin. Then show that the same intensity pattern is obtained for a slit that is not centred at the origin (i.e assume the slit edges are at x = a - b/2 and x = a +...

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...

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...

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= ...

Homework Statement Two speakers are 1.8m apart and point to each other. Each is emitting sound at a frequency of 680Hz. The sound waves are propagating at a speed of 340m/s. It can be neglected that the sound intensity is lowering with rising distance from the speaker. Define the wave...

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...

Homework Statement An atom trapping laser beam is incident on the trapping chamber as shown in the figure. Assume the lambda/4 plates and the miror are anti reflection coated. if the windows of the trapping chamber are uncoated, what is the intensit imbalance between incident and retro...

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...

need help urgent: calculating intensity 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...

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...