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प्रश्न
Define the term focal length of a lens.
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उत्तर
The distance from the optical centre O of the lens to its second focal point is called the focal length of the lens.
संबंधित प्रश्न
A student uses a lens of focal length 40 cm and another of –20 cm. Write the nature and power of each lens
Which one of the following materials cannot be used to make a lens?
Which has more power : a thick convex lens or a thin convex lens, made of the same glass? Give reason for your choice.
A converging lens has focal length of 50 mm. What is the power of the lens?
What is the nature of a lens whose power is, −4 D?
What is the unit of power of a lens? Define the unit of power of a lens.
Name the type of lens whose power is positive.
The image of an object formed by a lens is real, inverted and of the same size as the object. If the image is at a distance of 40 cm from the lens, what is the nature and power of the lens ? Draw ray diagram to justify your answer.
A screen is placed a distance 40 cm away from an illuminated object. A converging lens is placed between the source and the screen and its is attempted to form the image of the source on the screen. If no position could be found, the focal length of the lens
A stick partly immersed in water appears to be bent. Draw a ray diagram to show the bending of the stick when placed in water and viewed obliquely from above.
The same size images are formed by a convex lens when the object is placed at 20 cm or at 10 cm from the lens. The focal length of convex lens is ______ cm.
