What is the angular diameter (in arcseconds) of an object that has a linear diameter of 75 cm and a distance of 2 km?

The angular diameter is 77.35 arc-seconds.

Explanation:

The angular diameter, as shown in the figure, is the angle  subtended by the the diameter of the object.

Before we do the calculation, we first convert everything to meters.

The diameter of the of the object in meters is

75cm =0.75m,

and the distance to the object in meters is

2 km = 2000 m.

Now, from trigonometry we get:

and since 1 degree = 3600 arc-seconds, in arc-seconds is

so easy. just google the electromagnetic waves and it’ll pop up.