Lens Equation

A normal human eye has a focal length of about 0.023 m. If you look at the tip of a pencil, 0.553 m from your eye, how far is the image from the lens of your eye? 

• 0.024 m
• 0.033 m
• 0.045
• 0.055

The focal length of the lens in your eye is about 0.015 m. If the object is 1 m from your eye, where is the image produced? 

• 0.0315 m
• 0.0243 m
• 0.0152 m
• 0.0601 m

A converging lens produces an image twice the size of the original. If the object is placed 0.40 m from the lens, and the image produced is 0.80 m from the lens. What is the focal length of the lens? 

• 0.351 m
• 0.267 m
• 0.416 m
• 0.112 m

If the distance of the image from the lens (d_i) is positive. The image is considered....

• Real 
• Virtual

In the thin lens equation, do represents 

• Distance of the object from the lens
• Distance of the image from the lens