Intensity Definition and 898 Threads

Homework Statement A plane wave of amplitude A is incident on a surface of area S placed so that it is perpendicular to the direction of travel of the wave. The energy per unit time reaching the surface is E. The amplitude of the wave is increased to 2 A and the area of the surface is reduced...

Homework Statement a battery connected to a light bulb that has electrical resistance of (6 Ω) and the current intensity that gets through the bulb counts (12 A), if the internal resistance of the battery was (2 Ω):- 1- what is the Driving force of the battery (ε)? 2- if the light bulb was...

Homework Statement Show that the maximum intensity of 2 waves is worth (E_{01}+E_{02})^2 while for 2 waves out of phase by pi rad, it's worth (E_{01}-E_{02})^2. Homework Equations Not sure about intensity. According to my notes it's worth (U_1+U_2)(U_1+U_2)* where * denotes the complex...

Hello I am trying to understand Malus' Law and the Intensity of light. Let's say I have three polarizers. The first polarizer and the last polarizer have the same axis of polarization. The middle polarizer can be rotated to an angle \theta I know that Malus's Law for the intensity of light is I...

During my lecture we were presented with this problem How much louder is the intensity of sound at a rock concert in comparison with the sound of a whisper, if the two intensity levels (in dB) are 120 and 20, respectively? What my professor said was that the rock concert was 100 dB greater...

1. Unpolarized light with intensity 440 W/m2 passes first through a polarizing filter with its axis vertical, then through a polarizing filter with its axis 20.0 degrees from vertical. 2. Malus's Law 3. Ok, the intensity after going through the first polarizer should be 1/2...

1. A 200 mW horizontally polarized laser beam passes through a polarizing filter whose axis is 25 degrees from vertical. 2. Malus's Law 3. Ok, so I will use theta = 65 degrees in the I = I0cos(theta) equation, right? But how do I calculate I0 knowing only power and not area?

1. A beam of unpolarized light with intensity I_0 falls first upon a polarizer with transmission axis theta1 then upon a second polarizer with transmission axis theta2, where theta2 - theta 1 = 90 degrees (in other words the two axes are perpendicular to one another). What is the intensity I_2...

A source of sound emits 5.0 mW of acoustic power uniformly in all directions. 1. Calculate the intensity of this sound wave 10.0 m from the source. 2. Find the sound level in decibles 10.0 m from the source. Answers: 1. 4 x 10^-6 W/m^2 ---- I don't know how to get this answer. 2. 66 dB...

Homework Statement At a distance of 25m from an isotropic 100 MHz radio source the intensity is 120W/m2. A) What is the rms electric field at 25m? The answer should be 213 V/m. B) Over a 2 hour period, what is the momentum given to a 4cm x 4cm surface (at the 25m distance)...

Can someone help me to clear out a few questions about Intensity from spectral lines. - I have seen in many reports the unit cm-2 atm-1? Where does this come from? - What is the differences between line strength and the absolute intensity if the spectral line? - If you measure light from...

Accoding to US government regulations, the maximum sound intensity levels in the workplace is 90,0 dB. Within one factory, 32 ihdentical machines produce a sound intensity level of 92,0 dB. How many machines must be removed to bring the factory into compliance with the regulation? Possible...

Homework Statement You put a point source of light (S) a distance (d) in front of screen (A). How is the light intensity at the center of the screen changed if you put a completely reflecting mirror (M) a distance (d) behind the source? M-----d-----S-----d-----A Homework Equations...

Homework Statement It's a problem I'm having with my experiment. We set up a diode LASER through 2 polarizers, and changed one of the polarizers' angle with respect to the other, to demonstrate Malus's Law. We used some sort of photo detection device (which we were told uses the...

I've got an experiment coming up where I have to find out how the resistance in a circuit changes as more layers of 'tracing paper' are added onto a LDR i.e. as more paper is added the light intensity will fall and as a result the resistance through the circuit will increase. I am testing for...

A firework is detonated many meters above the ground. At a distance of 400m from the explosion, the acoustic pressure reaches a maximum of 10N/m2. Assume the speed of sound is constant at 343m/s, the ground absorbs all sound falling on it, and the air absorbs sound energy by the rate of 7dB/km...

Consider two loudspeakers (emitting sound waves of the same amplitude and wavelength of 15m) and an observer located in the x−y plane, with the two loudspeakers being at (2m, 0) and (−2m, 0), respectively, and the observer being at (0, 3m) initially. (i) Suppose the intensity of the combined...

Homework Statement A baby's mouth is 30 cm from her father's ear and 150 cm from her mother's ear. Compute the difference, in dB, between the sound intensity levels heard by the father and by the mother. Homework Equations Intensity = Power/ Area; power = 1/2 * mass per unit...

Homework Statement You are 10m away from a sound source. If you want the intensity in DB to double, you must move to a distance...? Homework Equations Idb = 10log(I/I0) I is proportional to 1/r^2 The Attempt at a Solution I know the answer is 1m and I know that in order to make...

Homework Statement How do you derive the following equation given I/Io= (I/N2)[(sinNØ/2)/(sinØ/2)]2 given that Ø= (2πdsinΘ)/λ Homework Equations Ø= (2πdsinΘ)/λ d=λ/sinΘ The Attempt at a Solution I have tried substituting Ø into the equation as well as d=λ/sinΘ, but I...

I am making a noise level meter, that would trigger an alarm, if the noise level has reached hazardous levels. However, one problem with noise is that it'd intensity decreases with distance, so that the meter would percieve a low sound near the meter and a high sound far away as equal. So does...

Homework Statement a)A sound wave with an intensity level of 80.1 dB is incident on an eardrum of area 0.600 10-4 m2. Calculate the energy is absorbed by the eardrum in 4.00 minutes in microJ b)The sound level 25.0 m from a loudspeaker is 69.0 dB. Calculate the rate at which sound energy is...

Homework Statement What is the intensity of sound wave with sound intensity level 34 dB? Homework Equations B = (10dB) log (I/Io) B = sound intensity level, I = intensity, Io= 1.0x10^-12 W/m^2 The Attempt at a Solution I figured it would be simply a matter of rearranging...

Homework Statement Five trumpet players have a sound intensity level of 75dB. What would be the sound intensity level of 30 such trumpet players? _______dB Homework Equations Increasing the sound intensity by a factor of 10 results in an increase in perceived loudness by approx. a...

Homework Statement What fraction of the acoustic power of a noise would have to be eliminated to lower its sound intensity level from 90 to 70dB? Homework Equations I = Power/Area B = 10 * log *(I/I0) I0 = 10-12W/m2 The Attempt at a Solution The answer I got for this is that the...

Homework Statement At a distance of 30 m the noise from the engine of an jet has an intensity of 130 dB. At this level, you will be in pain and your ears will hurt. That's why this intensity is know as the "pain threshold". How far do you have to be from a jet (total distance), in...

I need to convert the intensity, 130 counts per pixel into magnitudes per sq arc second. I have been given the radius as 5 arc sec, and a calibration constant, which is 30.8.

Homework Statement A tiny speaker emits sound with a frequency of 1000Hz evenly on all sides. On a distance of 1m from the loudspeaker is an amplitude variation of the particles of air 0.005 μm. On what distance we can barely hear the sound, if the limit of the audible strength or...

what is the relationship between amplitude and intensity...is intensity just the amplitude squared?

I've become interested in lasers and this question came to me today. Let's say we have two 10 mW lasers. One has a spot size of 1mm and one has a spot size of 10mm. Therefore, the first laser has a greater intensity. In classical physics we are told the wave amplitude increases. In modern...

I've been looking over an old exam for one of my classes, and cannot decipher the train of thought used in solving (or method used) the problem on the last page: http://people.physics.tamu.edu/kochar/FE/FE_Fall05_1.pdf Specifically, for the first part, what is going on...? Firstly, I have...

Homework Statement Harry and Sally are sitting on opposite sides of a circus tent when and elephant trumpets a loud blast. If Harry experiences a sound intensity level of 65dB and Sally only 55dB, what is the ratio of the distance between Sally and the elephant to the distance between the...

A^{2} \propto I When is it appropriate to use this formula? I don't understand how to use a proportionality. Say I have an amplitude A and I make it 2A can I use the equation to determine the intensity will increase by a factor of 4? I guess I don't know why it is a proportionality...

Homework Statement A sound wave with intensity 4 mW/m2 interferes destructively with a sound wave that has an intensity of 10 mW/m2. What is the intensity of the superposition of the two? Homework Equations sqrt of both values The Attempt at a Solution i believe that taking the...

Part of my independant investigation requires me to carry out an experiment, which when I graph results, would confirm Malus' Law. I plan on using a bulb as my ambient source and two polarizing lenses. I will then measure the intensity of the light after polarization. Hopefully, if i graph...

Homework Statement Light is emitted from a point source. How does amplitude of light change when light has traveled from R to 2R? Homework Equations Energy=(1/2)kA^2 where k is constant and A is amplitude Intensity=(Energy/time)/area The Attempt at a Solution My teacher...

Hi, If light intensity is determined by the number of photons, what determines the number of photons? A higher energy wave does not mean more photons, right? A higher energy wave just means that the photons have more energy, because higher frequency means more energy? How come a...

Homework Statement A spherical sinusoidal source radiates sound uniformly in all directions. At a distance 10.0m the sound intensity level is 1.00 × 10−4 W/m2. 1. At what distance from the source is the intensity 1.00 × 10−6 W/m2? A. 1 m B. 10 m C. 100 m D. 1 km 2. What is the...

okay so I am having trouble with my sound ISU (independent study unit). Though my teacher said he would help, when i asked he said he cant... what i need to find is the sound intensity for the following decibel values.. a) 100dB b) 55dB now the only relevant equation would be \beta= 10...

Homework Statement A line source of sound (for instance, a noisy freight train on a straight track) emits a cylindrical expanding sound wave. Assuming that the air absorbs no energy, find how (a) the intensity I and (b) the amplitude sm of the wave depends on the perpendicular distance r from...

The higher the intensity of the light we will get a higher stopping potential. Why is that so? is there any theory and formula to justifiy this behavior? How is wavelength affecting the intensity of light? Please advise. Thank You

1. If the human ear can detect sound of an intensity of 10^{-12} given a power source of 50W what is the maximum distance the sound could theoretically be heard 2. I = \frac{P}{A} A = 4\pir^{2} 3. Just used first equation to get the area and from that the radius and therefore...

Homework Statement The stress intensity factor is defined as: \Delta K_1(m,a(m))=\Delta q(m)\sqrt{\pi*a(m)} My question is: is \Delta K_1(m,a(m)) the same as \Delta K_1(m) Because my book says: ''\Delta K_1(m) is the mode 1 stress intensity factor'' is that just the same as: \Delta...

Homework Statement To waves with the same frequency interfere. The intensity of the two waves are I1 and I2. Show that the resultant intensity is: I = I1 +I2 + 2*sqrt(I1*I2)*cos(δ) Where δ is the phase difference between the two waves. Hint: Use the relation between intensity and...

Homework Statement An elevator, with people in it, has a mass of 1400 kgs. The motor is hooked up to the power grid that provides 220 volts of power. The elevator has to go up 30 meters at 4m/s. How many watts of potential (not sure if it's called that) are required to get the elevator...

Unpolarized light from an incandescent lamp has an intensity 176 Cd as measured by a light meter. What is the intensity reading on the meter when two ideal are inserted between the bulb and the meter with their axis of polarization making an angle of θ = 40.0° relative to each other? Express...

Hi, I'm trying to find out how changing the current fed through to a filament (e.g. sodium) of a lamp would change the light intensity. To determine the relationship, I will first need to find out how to measure the intensity of light. I've thought of one possible way to do it, but the...

Hey people, I'm struggling to understand exactly what Electric Flux Density D and Electric Field Intensity E are. So far, my understanding is that D depends on relative permittivity, while E depends only on the permittivity of free space. Also, I understand that D reflects only the free...

Homework Statement Two sheets of Polaroid are placed on top of each other with an angle φ between their pass directions. Calculate be the ratio of transmitted to incident intensity for initially unpolarised light if φ = 30°.I copied the question exactly, I'm pretty sure that typo wasn't on...

How would I go about converting 59.7 mw/m^2 to lux? I would appreciate any help I can't find an equality.