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# noob question, make you feel smart, or me stupid

#### ShaOwned

##### New member
milliradian. standard unit to measure divergence of a propagating beam

#### ZackTman

##### New member
...lol what divergence

#### ShaOwned

##### New member
Okay so all beams, contrary to uneducated opinion, don't go straight.

Basically after they exit the lens, they will focus down to one spot, then "spread out."

The less spreading that occurs, the smaller the dot will be at long distances.

Anything else?

#### ZackTman

##### New member
so mrad is where the beam is the smallest after leaving the focusing lense?

#### ZackTman

##### New member
so say a laser has .5mrad then the smallest point is .5 mrads away form he lense?

#### ShaOwned

##### New member
Not quite. Mrad is a unit to measure the divergence (spread) of the beam.

Where the beam is smallest is called the focal point

#### ShaOwned

##### New member
Radians is an angle. .5 Mrad means that that is the angle at which the beam gets larger the farther away from the focusing lens

#### ZackTman

##### New member
oh so mrad is how storng the laser is at the focal point

Troll.

#### aryntha

##### New member
Milliradians, a division of radians, it's a standard angle measurement. Used in a lot of fields, not just lasers. Especially if you're talking about deviations less than a degree - specifically small divergences over long distances. (Satellites/microwave, astronomy, lasers of course, and in some cases firearms.) If you have a circle of radius x, one radian is the angle that occurs when the outer arc length is equal to the radius of that circle.

One milliradian would be 1/1000th of that. If your laser source point (diode or OC mirror) is the 'center of the circle', and x measurement along your beam is the radius, the width of the beam at x feet would be your arc length.

The angle developed between source point, along beam of specified (x) distance when the beam is at thickness gives you your mRad reading.

so radians=n divided by x; or radians = width of beam at distance x, divided by x. (same units.) With a laser that number will be far <1, so you'd measure it in milliradian or millirads.

EDIT: Guess it was a troll, but, leaving it here for future searches.

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#### ZackTman

##### New member
thanks for your guys time. i understand now

#### Asherz

##### New member
Really? Because most of those explanations were ridiculously complicated.

Mrad is a way of measuring divergence, divergence is the rate at which the beam gets wider and wider the further away it goes. Mrad is basically measuring how quickly the beam gets wider.

Little diagram to help

#### chipdouglas

##### Well-known member
i feel like i'm on an episode of "punked", where Ashton? LoL

michael

#### ShaOwned

##### New member
Really? Because most of those explanations were ridiculously complicated.
QUOTE]

Mrad is a unit to measure the divergence (spread) of the beam.
I don't see what's complicated about that.