Below is a concise list of key definitions from Chapter 10: Optical Instruments

Below is a concise list of key definitions from Chapter 10: Optical Instruments of the 11th Class Physics syllabus for the Federal Board of Intermediate and Secondary Education (FBISE), aligned with the National Book Foundation (NBF) curriculum. These definitions cover the essential concepts related to optical instruments as typically presented in this chapter.

1. Optical Instrument: A device that uses the principles of optics to manipulate light for purposes such as magnification, observation, or measurement (e.g., microscope, telescope).
2. Lens: A transparent optical element with curved surfaces that refracts light to converge or diverge it.
3. Converging Lens (Convex Lens): A lens that causes parallel rays of light to converge at a focal point.
4. Diverging Lens (Concave Lens): A lens that causes parallel rays of light to diverge, appearing to originate from a focal point.
5. Focal Point: The point where parallel rays of light converge (for a converging lens) or appear to diverge from (for a diverging lens) after refraction.
6. Focal Length (f): The distance from the center of a lens to its focal point, measured in meters.
7. Principal Axis: An imaginary line passing through the optical center of a lens, along which light rays pass without deviation.
8. Optical Center: The central point of a lens where light rays pass through without bending.
9. Magnification (M): The ratio of the size of the image to the size of the object, given by M = h_i/h_o or M = -i/o, where h_i is image height, h_o is object height, i is image distance, and o is object distance.
10. Lens Formula: The relationship between object distance (u), image distance (v), and focal length (f) for a lens, given by 1/f = 1/u + 1/v.
11. Power of a Lens: The ability of a lens to converge or diverge light, given by P = 1/f, where f is in meters, measured in diopters (D).
12. Simple Microscope: A single convex lens used to magnify small objects, producing a virtual, enlarged image.
13. Compound Microscope: An optical instrument with two convex lenses (objective and eyepiece) used to produce a highly magnified image of small objects.
14. Objective Lens: The lens in a microscope or telescope closest to the object, forming a real, magnified image.
15. Eyepiece (Ocular Lens): The lens in a microscope or telescope closest to the observer’s eye, used to view the image formed by the objective lens.
16. Astronomical Telescope: An optical instrument with two convex lenses (objective and eyepiece) used to observe distant celestial objects, producing a magnified image.
17. Terrestrial Telescope: A telescope designed for observing earthly objects, incorporating an erecting lens to produce an upright image.
18. Galilean Telescope: A telescope with a convex objective lens and a concave eyepiece, producing an upright image, used for terrestrial observations.
19. Angular Magnification: The ratio of the angle subtended by the image to the angle subtended by the object when viewed with the naked eye.
20. Resolving Power: The ability of an optical instrument to distinguish between two closely spaced objects as separate entities.
21. Spectrometer: An optical instrument used to measure the properties of light (e.g., wavelength) by dispersing it into a spectrum.
22. Least Distance of Distinct Vision (D): The minimum distance at which the human eye can see objects clearly, typically taken as 25 cm.
23. Near Point: The closest distance at which the eye can focus on an object clearly, varying with age.
24. Far Point: The farthest distance at which the eye can focus on an object clearly, typically infinity for a normal eye.

These definitions encapsulate the core concepts of optical instruments from Chapter 10 of the FBISE 11th Class Physics curriculum. If you need further explanation or additional terms, please let me know!