What is a critical angle and when does total internal reflection take place?

When a ray of light travels from a denser medium to a rarer medium it bends away from the normal. It the angle of incidence is too large, the angle of refraction will be very large as well (It can be proved by Snell's law). If the value of angle of incidence is higher than a certain value which is known as the critical angle, the ray of light doesn't travel to the rarer medium instead it gets internally reflected in the denser medium. The value of critical angle can be calculated by the following formulae. 

Critical angle = arcsin(nr/ni

Where nr is the refractive index of the rarer medium, ni is the refractive index of the denser medium and arcsin is sine inverse. 

Swapnil S. GCSE Maths tutor, GCSE Physics tutor, GCSE Chemistry tutor...

2 years ago

Answered by Swapnil, a GCSE Physics tutor with MyTutor

Still stuck? Get one-to-one help from a personally interviewed subject specialist


£22 /hr

Anna W.

Degree: Medicine (Other) - Edinburgh University

Subjects offered:Physics, Dutch+ 5 more

-Personal Statements-
-Medical School Preparation-

“Hi! I am Anna and I am studying Medicine. I have done the IB (new syllabus) so I know all about the new curriculum, including IAs and Explorations! ”

£18 /hr

Joseph B.

Degree: Accounting and Finance (Bachelors) - LSE University

Subjects offered:Physics, Maths+ 1 more

-Personal Statements-

“Previously I have found that all pupils learn differently, so need to be taught differently, thus, tailoring my lessons to suit individuals.”

MyTutor guarantee

£20 /hr

Dan B.

Degree: MPhys Physics (Masters) - Exeter University

Subjects offered:Physics, Maths


“Hi I'm Dan and I'm in the first year of a four-year MPhys Physics degree at the University of Exeter. I am very patient and will tailor the sessions' content and pace to suit your individual needs...”

About the author

£18 /hr

Swapnil S.

Degree: BEng (Hons) Electrical and Electronics Engineering (Bachelors) - Manchester University

Subjects offered:Physics, Maths+ 2 more

Further Mathematics

“Top tutor from the renowned Russell university group, ready to help you improve your grades.”

MyTutor guarantee

You may also like...

Posts by Swapnil

What can I say about the roots of a quadratic equation without actually calculating them?

What is a critical angle and when does total internal reflection take place?

Why are elements of group 0 chemically inert?

Other GCSE Physics questions

What is an (electrostatically) induced charge?

How does electromagnetic induction produce a current?

How does conduction work in metals?

Explain the process of nuclear fission.

View GCSE Physics tutors

We use cookies to improve your site experience. By continuing to use this website, we'll assume that you're OK with this. Dismiss