Calculates the width of a radar beam as a function of range and beam angle.

`beam_width(range, beam_angle = 1)`

## Arguments

- range
numeric. Range (distance from the radar antenna) in m.

- beam_angle
numeric. Beam opening angle in degrees, typically the
angle between the half-power (-3 dB) points of the main lobe

## Value

numeric. Beam width in m.

## Examples

```
#' # beam width in meters at 10 km range:
beam_width(10000)
#> [1] 174.5241
# define ranges from 0 to 1000000 meter (100 km), in steps of 100 m:
range <- seq(0, 100000, 100)
# plot the beam width as a function of range:
plot(range, beam_width(range), ylab = "beam width [m]", xlab = "range [m]")
```