Chapter 30, Problem 28A

Copy the three drawings in the figure. Then use ray diagrams to find the image of each arrow.

To determine

Ray diagrams to find image formed by lens

Explanation of Solution

Introduction:

Image formed by concave lens is depends on position of an object from lens. If an object far away from focal point of concave lens image is real, behind the lens and upside down. If an object distance from lens is less than or equal to the focal length of lens, image is virtual and upright.

Image formed by convex lens is always virtual, nearer to lens than the object, smaller than the object and right-side up.

To draw ray diagram for lens there are three rays are useful:

• A ray which is parallel to the principal axis that refracts by lens and passes through the focal point of opposite side
• A ray which is passing through the center of lens and its direction is not changed
• A ray which is passing through the focal point that reflects by lens and travels parallel to the principal axis

Concept:

  

Conclusion:

Hence, we can say that image formed by convex lens is virtual, while image formed by concave lens is depends on position of an object.