What is the electric field strength of the laser light at the focus point?
Intensity I(peak) = energy/(area*time) = 9.82438E13 W/m^2 E = sqrt(I(peak)*Z0) = 192383516.88676 V/m (where free-space impedance Z0 = sqrt(µ0/e0) = 376.730313462204 ohms)
Physics help please. power, energy, intensity?
A 0.90-mW laser emits a narrow beam of light that enters the eye. (a) How much energy is absorbed by the eye in 0.2 s? mJ (b) The eye focuses this beam to a tiny spot on the retina, perhaps 4.0 μm in diameter. What is the average intensity of light (in W/cm2) at this spot? Incorrect: Your answer is incorrect. Your response differs significantly from the correct answer. Rework your solution from the beginning and check each step carefully. W/cm2 (c) Damage to the retina can occur if the average intensity of light exceeds 1.0 ✕ 10−2 W/cm2. By what factor has the intensity of this laser beam exceeded the safe value?
Does intensity of light decrease with increase in distance?
Thats an interesting question. The answer is Yes AND No depending on how you look at the problem. The most common case where the answer is YES occurs when you have a “point” source which emits in all directions. You can think of the light as a spherical shell expanding from the source.If you could somehow measure the total intensity over the entire shell, then the total energy and hence intensity would remain constant, even as the shell expands. But of course, that’s not how we typically measure the light. We would measure it at some limited point in space. Hence as the shell gets larger as it moves further from the source, the measured intensity at one point on the shell tends to reduce inversely as the square of the distance from the source.However, if you look at a laser beam for example. A laser is essentially a device that emits photons in approximately a single direction. Hence, the intensity remains constant (approximately) over distance. It will eventually start to decrease as diffraction spreads the beam.If you pass light through a lens which is set up to focus the light to a spot, the intensity of the measured beam will INCREASE as distance increases ….up to a certain distance and then it will start to decrease.This basically helps us understand what is really happening. Ultimately, light is emitted as a number of discrete photons. A single photon, like any particle, simply travels in a given direction and it conserves its energy/intensity as it moves. Hence, when we view light as single photons, the intensity of a single photon does NOT decrease with distance. However, if the light source emits a large number of photons, although each photon preserves its energy as it travels, the spatial distribution of the ensemble of photons may well change, so when we see light spreading out from a point source, what we are saying is that the number of photons at any one point in space is dropping off with distance, hence the measured intensity falls off. But the energy of any single photon remains constant.
Power, energy, intensity?? physics help needed?
A 0.90-mW laser emits a narrow beam of light that enters the eye. (a) How much energy is absorbed by the eye in 0.2 s? mJ (b) The eye focuses this beam to a tiny spot on the retina, perhaps 4.0 μm in diameter. What is the average intensity of light (in W/cm2) at this spot? (c) Damage to the retina can occur if the average intensity of light exceeds 1.0 ✕ 10−2 W/cm2. By what factor has the intensity of this laser beam exceeded the safe value?
Interference of light waves?
Interference of light waves: a)focuses a broad beam of light into a point b) creates a pattern of light and dark regions c)separates light into its component colors d) bends light as it passes the edge of an object Which of the above is correct? Thanks
Different types of Lasers ??
the different types of lasers are continious lasers and non continious. eg: helium neon, diode laser, argon. krypton, neon lasers etc...
If I aim a laser pointer to the sky, would the light of the laser go into space? And if so, will it travel for all eternity? Does light travel infinite?
If you have a powerful enough laser, then it will reach space, but none of the common laser pointers available for sale to the public will manage it. In theory if the laser light makes it into space, it will go on forever or until it is absorbed by something. In reality it won't get very far before it is undetectable. The Inverse-square law says that the intensity of electromagnetic waves (including light) is inversely proportional to the square of the distance from the source. This means the light beam spreads out spherically until it is so weak that it can't be detected. NASA placed special reflectors on the Moon during the Apollo missions in the '60s and early '70s for the Lunar Laser Ranging experiment. To measure the distance to the Moon, they fire a very powerful laser at these reflectors on the Moon and measure how long it takes light to bounce back. The lasers are enormously more powerful than your garden variety laser pointers, but even so, the beam has spread out to about 6.5 kilometers wide when it hits the Moon. The reflected light can be identified as originating from the laser because the laser is highly monochromatic, but it is too weak to be seen with the human eye: out of [math]10^{17}[/math] photons aimed at the reflector, only one will be received back on Earth every few seconds, even under good conditions.
Physics Question 8 Best Answer=10points?
A laser beam has intensity I0. What is the intensity, in terms of I0, if a lens focuses the laser beam to 1/10 its initial diameter? ( I know this is 100 so you can ignore this) What is the intensity, in terms of I0, if a lens defocuses the laser beam to 10 its initial diameter?