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Optical instruments are any devices that use a single or several lenses to collect light as an input and perform any action on it, such as enhancing an image for clearer viewing or enlarging it, depending on the equipment’s function. All popular optical tools employ one of two types of lenses.
Early types of telescopes, produced when the need to study the planets and their moons, as well as other celestial bodies, were the first optical equipment to be utilised. The Italian astronomer and physicist Galileo di Vincenzo Bonaiuti de’ Galilei, also known as Galileo Galilei, is credited with inventing the first telescope. The Father of Observational Astronomy, as he is known.
The microscope, which is used to examine very small particles and creatures, is another prominent optical equipment. A Dutch eyeglass manufacturer named Zacharias Janssen invented the first microscope. The Dutch scientist Antonie Philips van Leeuwenhoek is known as the Father of Microbiology because of his extensive study in the realm of microscopy. Both the telescope and the microscope work on the principle of image enhancement, which enlarges a small object so that it may be examined and analysed more easily.
Q1. A little youngster wears spectacles with a focal length of -50 cm. Give the name of the eyesight problem that he has.
a) Astigmatism
b) Hypermetropia
c) Myopia
d) Presbyopia
Answer: c)Myopia because the lens employed is concave because the focal length is negative. When a person is prescribed a concave lens, they are said to have myopia. As a result, the boy suffers from myopia.
Q2. When the diameter of a telescope’s objective is doubled, how much does the image’s intensity increase?
a) Two times
b) Four times
c) Eight times
d) Sixteen times
Answer: b)Four times because the area of the objective rises fourfold when the diameter is doubled. Its light-gathering capacity increases by fourfold. The brightness of the image has also been boosted by four times. As a result, the image’s intensity increases by a factor of four.
Q3. A fly is perched on the telescope’s objective. What influence will it have on the faraway object’s final image?
a) Reduces
b) Increases
c) Remains constant
d) Indefinite
Answer: a)Reduces because In the final image, the fly will not be seen. However, because light does not enter the telescope from the region of the object where the fly is sitting, the final image’s intensity is diminished. As a result, the final photograph of the fly will show a reduction effect.
Q4. A telescope will be constructed using two lenses with focal lengths of 5 cm and 50 cm. For the objective, which lens will you use?
a) Both
b) Neither
c) 5 cm
d) 50 cm
Answer: d)50cm because the objective in a telescope should have a longer focal length than the eyepiece. As a result, the objective will be a 50 cm focal length lens. As a result, the eyepiece will be the smaller of the two, namely the 5 cm focal length lens.
Q5. Which of the following is used to extend a telescope’s range?
a) Increasing the focal length
b) Decreasing the focal length
c) Increasing the diameter of the objective
d) Decreasing the diameter of the objective
Answer: c) Increasing the diameter of the objective because the objective’s light-gathering power will improve, allowing even faint objects to be seen. This is accomplished by increasing the objective’s diameter. As a result, the range of the telescope can be expanded by increasing the diameter of the objective.
Q6. The upper portion of a bi-focal lens is convex, while the lower portion is concave.
a) True
b) False
Answer: b)False because the upper section of a bi-focal lens should be concave, while the lower part, which is utilised for distance vision, should be convex. A bi-focal lens like this is used for reading.
Q7. Humans are unable to perceive objects in ultra-violet light, but ‘X’ can. Determine the identity of X.
a) Penguin
b) Bees
c) Ant
d) Tiger
Answer: b)Bees because Bees have retinal cones that are sensitive to ultra-violet light, allowing them to see objects in this wavelength range. Ultraviolet blindness is a condition that occurs in humans. As a result, although humans are unable to perceive UV light, bees can.
Q8. When the diameter of a telescope’s objective is increased, how does the magnifying power of the telescope change?
a) Independent
b) Doubled
c) Halved
d) Becomes zero
Answer: a)Independent because The formula m = fo/fe is used to calculate the magnifying power of a telescope. The focal length of the object is fo, while the focal length of the eyepiece is fe . It is unaffected by the object’s aperture. As a result, increasing the diameter of the objective has no effect on the magnifying power.
Q9. For someone whose least distance of distinct vision is 50 cm, what focal length reading spectacles should they have?
a) + 25 cm
b) – 25 cm
c) + 50 cm
d) – 50 cm
Answer: d)50 cm because By thin lens formula,
1/f = 1/v – 1/u
1/f = 1/(-50) – 1/(-25)
f= -50 cm.
Q10. A basic microscope with a power of 10 D is used to examine an object. To limit maximum angular magnification, where should the object be placed? The minimum distance for clear vision is 25 cm.
a) + 7.1 cm
b) – 7.1 cm
c) + 25 cm
d) – 25 cm
Answer: b)7.1 cm because Angular magnification is maximum when the final image is formed at the near point.
1/u = 1/v – 1/f
1/u = -1/25 – 1/10
u = -7.1 cm. To avoid angular magnification, the object should be placed 7.1 cm in front of the lens.
Q11. Which of the following autocollimator assertions is false?
a) Has an infinity telescope
b) Has an autocollimator
c) For smaller angle it is not accurate
d) Very high sensitivity
Answer: c)For smaller angles it is not accurate because An autocollimator is a type of optical equipment used to evaluate minor angular changes. For small angular measurements, the Autocollimator provides an extremely sensitive and precise method. An autocollimator is a combination of an infinity telescope and a collimator.
Q12. What is the connection between reflector tilt and the linear displacement of the graticule image in the eyepiece plane?
a) Both are independent of each other
b) Linear displacement is directly proportional to the reflector tilt
c) Linear displacement is inversely proportional to the reflector tilt
d) Linear displacement is directly proportional to the square of the reflector tilt
Answer: b)Linear displacement is directly proportional to the reflector tilt because the tilt of the reflector is precisely proportional to the linear displacement of the graticule image. It can be measured directly in angular units using an ocular graticule, electronic detector device, or optical micrometre.
Q13. In an autocollimator, what is the primary function of the steel cube reflector?
a) To provide a 90-degree standard in 3 planes
b) For general bench use
c) Calibrate surface plate
d) For setting but not checking perpendiculars
Answer: a)To provide a 90 degree standard in 3 planes because A steel cube reflector can be used for a variety of purposes. In three planes, it can be utilised to provide a 90-degree angle standard. Perpendiculars can be set or checked with this tool.
