Lecture_5_1-22_

Lecture_5_1-22_ - Angular measure See box E-1 in text...

This preview shows pages 1–9. Sign up to view the full content.

Angular measure • See box E-1 in text • Around a whole circle = 360 o = 360 degrees •( The Earth moves about 1 o per day around the Sun.) •1 o is divided into 60 arc minutes = 60’ • 1’ is divides into 60 arc seconds = 60” • Do not confuse arc minutes and seconds with minutes and seconds of time

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Some angles in the sky.
An object appears at a larger angle when it is closer Angular size in radians = size/distance See box E-2 for details Since we can measure the angle with a telescope, if we know the size of an object, we can find its distance, and vice-versa. We won’t do any calculations with this, but you need to know the concept, and the units of angular measure.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Fig E.20 in text Fig 10.1 in text Using parallax to measure distances to astronomical objects
Using Parallax • The radius of the Earth’s orbit is defined as 1 astronomical unit = 1 AU = 93,000,000 miles • Using the baseline of the diameter of the Earth’s orbit = 2 AU, measure the parallax angle to get the distance to the star

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Parsecs as distance • Parallax angles are small – all less than 1 arc second • The distance for which the parallax would be 1” is called a “parsec”. • Parsec is a common astronomical unit of distance equal to about 3.3 light-years.
Reflection and Refraction Law of reflection Angle of incidence = angle of reflection Law of refraction n 1 sin ± 1 = n 2 sin ± 2 N = index of refraction

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Both a positive lens (thicker in the middle) and a concave mirror can converge parallel light to an approximate focus. (The simple lens has color errors in its focus, and it takes
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 28

Lecture_5_1-22_ - Angular measure See box E-1 in text...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online