Why is a convex lens with smaller focal length and not a longer one used as a magnifcation glass
Asked by Trisha Gupta | 10th Oct, 2021, 03:27: PM
Figure given above shows the formation of magnified image , when object is placed between lens and focal point .
Image-1 is formed if focal point is F1. Similarly image-2 is formed if long focal length lens with focal point F2 is used
Magnification of image depends on the angle subtended by the light ray passing through the focal point at
other side of lens with respect to object.
As seen from figure , subtended angle θ is greater if focal length is less. We see from figure if focal point is F1,
then subtended angle θ1 is greater compare to subtended angle θ2 at Focal point F2 .
Hence magnification of image-1 is greater than that of image-2 .
Since magnitude of magnification is important in optical microscope, smaller focal length is used as objective lens
Answered by Thiyagarajan K | 10th Oct, 2021, 05:01: PM
- Please answer this
- State three characteristics of the image formed by a convex lens when the object is close to it.
- Explain about lenses
- A 4.0 cm tall object is placed perpendicular ( e.at 90) to the principal axis of a convex lens of food length 10 cm . The distance of the object from the lens is 15cm. Find the math, position and size of the image.Also find its magnification.
- Why is object placed between 2f1 and f1 in a convex lens projector ?
- 35. A student focuses the image of a candle flame, placed at about 2 m from a convex lens of focal length 10 cm, on a screen. After that he moves gradually the flame towards the lens and each time focuses its image on the screen. (A) In which direction does he move the lens to focus the flame on the screen? (B) What happens to the size of the image of the flame formed on the screen? (C) What difference is seen in the intensity (brightness) of the image of the flame on the screen? (D) What is seen on the screen when the flame is very close (at about 5 cm) to the lens?
- How many types of image forms due to lenses ? What are those ? Mention the differences
- An object 50cm tall is placed on the principal axis of a convex lens.Its 20cm tall image
- How does the size of image change as the object is brought from closer to infinite towards the convex lens?
Kindly Sign up for a personalised experience
- Ask Study Doubts
- Sample Papers
- Past Year Papers
- Textbook Solutions
Verify mobile number
Enter the OTP sent to your number