optical instrument

An optical instrument uses eye-lens of power 16 D and objective lens of power 50D and has a tube length of 16.25 cm. Name the optical instrument and calculate its magnifying power if forms the final image at infinity.

( A ) Vernier callipers with 20 divisions on sliding scale, coinciding with 19 main scale divisions ( B ) A screw gauge of pitch 1 mm and 100 divisons on the circular scale ( C ) An optical instrument that can measure length to within a wavelength of light Out of A , B and C the most precise devide for measuring length is

Which of the following is correct? (A) The size of image on the retina is roughly proportional to the angle subtended by the object on the eye. This angle is known as visual angle. The optical instruments are used to increase the visual angle (B) In normal adjustment, eye is least strained and final image is formed at infinity (c) The magnifying power is written with a unit X (D) All options are correct

Instruments

Instruments

Which of the following musical instrument is a reed instrument?