Optics — Class 11 Maharashtra HSC Physics revision notes
A 7-page visual revision sheet for Optics, written for Class 11 Maharashtra HSC Physics. Formulas, diagrams and the traps that cost marks, laid out to be read the night before rather than the term before. Free, and it opens inside CapCompass.
Page 1 as PDF
Optics in one look
light bends at every boundary it crosses, and geometrical optics is just bookkeeping for exactly how much
Light, and the four laws behind ray optics
- light: an electromagnetic wave that also carries energy as photons, a dual nature
- each picture explains its own set: ray optics for mirrors, lenses, prisms
- wave optics: interference, diffraction. particle nature: photoelectric effect
- four laws: straight lines in a homogeneous, isotropic medium; crossing rays don't disturb each other
- reflection: angle of incidence = angle of reflection. refraction: Snell's law
- straight travel, reflection, refraction all follow from Fermat's least time; ray independence is a separate assumption
Multiple images between two inclined mirrors
- for two plane mirrors at angle θ, let n = 360°/θ
- n even: number of images N = n - 1, whatever the object's position between them
- n odd, object on the bisector: N = n - 1
- n odd, object off the bisector: N = n
- n not a whole number: N is the integer part of n
- all the images lie on one circle through the object, centred where the mirrors meet
Cartesian sign convention
- distances from the pole, incident light drawn left to right
- along the incident light positive, against it negative
- heights above the principal axis positive, below negative
- a real object sits left of the pole: u is always negative
Spherical mirrors
- focal length, radius of curvature
f = R/2 - mirror formula
1/v + 1/u = 1/f - lateral magnification
m = -v/u - focal power, in dioptre
P = 1/f
Spherical aberration
- f = R/2 and one sharp focus: paraxial rays only
- outer rays focus nearer the pole: a blur, the circle of least confusion
- a parabolic mirror has none: parallel rays meet at one focus
- so searchlights, torches, headlights, reflecting telescopes use parabolic mirrors
Page 1 of 7. The full sheet, all 7 pages, opens free in the app.
What this Optics sheet covers
- Light, and the four laws behind ray optics
- Multiple images between two inclined mirrors
- Cartesian sign convention
- Spherical mirrors
- focal length, radius of curvature
- mirror formula
- lateral magnification
- focal power, in dioptre
- Spherical aberration
- Mirror ray diagrams, drawn from the mirror formula
- Concave mirror, object position and image
- Refractive index, and real vs apparent depth
- absolute refractive index
- relative refractive index, medium 2 with respect to 1
- seen from above through a plane surface
- Critical angle and refraction at a spherical surface
- critical angle, denser medium of relative index n
- one spherical surface, media n_1 then n_2, radius R
- Total internal reflection
- Optical fibre
- Mirage
- Where total internal reflection is put to work
- Prism binoculars
- Periscope
- Diamond
- Thin lens formula and lensmaker's equation
- thin lens formula
- lensmaker's equation
- lenses in contact
- Prism formula, thin-prism deviation, dispersive power
- prism angle A, minimum deviation δ_m: i=e, r_1=r_2=A/2
- thin prism (A under 10 degrees), deviation is constant
- dispersive power, extreme colours violet and red, yellow as mean
- Primary vs secondary rainbow
- Primary
- Secondary
- Two prisms: crown and flint
- thin prism: angular dispersion, violet to red
- no dispersion, flint turned over
- no deviation of the mean colour
- Lens aberrations, and the achromatic fix
- Magnifying power, the key idea
- Simple and compound microscope
- simple microscope, image at infinity (minimum M)
- simple microscope, image at D (maximum M)
- compound microscope, normal adjustment
- Astronomical telescope, normal adjustment
- magnifying power
- length of the telescope
- Symbols
- Combinations: lenses, lens and mirror, silvered lens
- Traps that cost marks
- Tricks that save time
How CapCompass uses this sheet
These notes are not a standalone PDF. CapCompass plans Physics chapter by chapter against your real exam dates and free hours, and when the plan reaches Optics the sheet opens inside the study block itself — at the page covering the sub-topic that block is on, with the timer still running. Revision arrives at the moment the plan says revise, instead of having to be gone looking for.