CBSE Class 10: Refraction Through Spherical Lens Videos | Image formation by convex lens

• what is a lens?
• The power of convex lens of focal length 20 cm is
  
• A lens of focal length 12cm forms an erect image three times the size of the object. What is the distance between the object and image? 
• Please answer this  
  
• State three characteristics of the image formed by a convex lens when the object is close to it.
• Explain about lenses
• Why is a convex lens with smaller focal length and not a longer one used as a magnifcation glass
• 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?

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