There are some rules which we use to obtain images in a ray diagram

Let's look at them


Rule 1 - Ray parallel to principal axis will pass through focus

Rule 1 - Ray parallel to principal axis will pass through focus 2 - Teachoo.jpg

For a convex lens ,

we see that ray passes through focus on right side

For a concave lens,

we see that ray appears to pass through focus on left side

 

Rule 2 - Ray passing through focus will become parallel to principal axis

Rule 2 - Ray passing through focus will become parallel to principal axis - Teachoo.jpg

For a convex lens,

we see that ray passing through focus on left becomes parallel to principal axis after refraction

 

For a concave lens ,

since focus is on the right side,

it appears that ray passes through focus, and then it becomes parallel to principal axis

 

Rule 3 - Ray passing through Optical Center will emerge without deviation

Rule 3 - Ray passing through Optical Center will emerge without deviation - Teachoo.jpg

For a both convex and concave lens,

we see that ray passing through Optical center emerges without deviation

 

  1. Class 10
  2. Chapter 10 Class 10 - Light - Reflection and Refraction

About the Author

Davneet Singh's photo - Teacher, Computer Engineer, Marketer
Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.