Microscope and astronomical telescope
- A microscope has an objective of focal length 2 cm, eyepiece of focal length 4 cm and the tube length of 40 cm. If the distance of distinct vision of eye is 25 cm, the magnification in the microscope is Answer: 2. 125 Key idea: for a compound microscope, the magnification is the product of the objective magnification and the eyepiece magnifi... 1
- A small telescope has an objective of focal length 140 cm and an eye piece of focal length 5.0 cm. The magnifying power of telescope for viewing a distant object is: Answer: 3. 28 Key idea: For a telescope in normal adjustment (distant object), m=f_o/f_e . m=140/5.0=28 . Option 3. 1
- A lens of large focal length and large aperture is best suited as an objective of an astronomical telescope since : Answer: 4. all of the above. Key idea: for a telescope objective, large focal length gives larger magnification, and large aperture helps th... 1
- Assume that light of wavelength 600 nm is coming from a star. The limit of resolution of telescope whose objective has a diameter of 2 m is : Answer: 1. 3.66×10⁻⁷ rad Limit of resolution of a telescope: Δθ=1.22λ/D . Δθ=frac1.22×600×10⁻⁹2=3.66×10⁻⁷\ rad Answer: option 1. 1
- An astronomical refracting telescope will have large angular magnification and high angular resolution, when it has an objective lens of Answer: 2. large focal length and large diameter Angular magnification of an astronomical telescope is m=f_o/f_e , so a large objective foca... 1
- The ratio of resolving powers of an optical microscope for two wavelengths λ_1 = 4000 and λ_2 = 6000 is : Answer: 2. 3 : 2 Key idea: resolving power of a microscope is ∝dfrac1λ . R₁/R₂=λ₂/λ₁=6000/4000=3/2 , i.e. 3 : 2. 1
- A astronomical telescope has objective and eyepiece of focal lengths 40 cm and 4 cm respectively. To view an object 200 cm away from the objective, the lenses must be separated by a distance : Answer: 4. 54.0 cm Key idea: the objective forms an image of the nearby object; the eyepiece must focus on that image (final image at infini... 1