Explore the principles of light behavior, including reflection and refraction, and understand how these phenomena shape our perception of the world.
Light – Reflection and Refraction – Formula & Equation Sheet
Essential formulas and equations from Science, tailored for Class X in Science.
This one-pager compiles key formulas and equations from the Light – Reflection and Refraction chapter of Science. Ideal for exam prep, quick reference, and solving time-bound numerical problems accurately.
Key concepts & formulas
Essential formulas, key terms, and important concepts for quick reference and revision.
Formulas
Mirror Formula: 1/v + 1/u = 1/f
v is image distance, u is object distance, and f is focal length of the mirror. This formula relates the positions of the object and image to the mirror's focal length. Used to find image location.
Magnification (m) = h'/h = -v/u
h' is image height, h is object height, v is image distance, u is object distance. Negative sign indicates inversion. Determines size and nature of the image.
Refractive Index (n) = c/v
c is speed of light in vacuum, v is speed of light in medium. Measures how much light bends when entering a medium. Higher n means more bending.
Snell’s Law: n₁ sinθ₁ = n₂ sinθ₂
n₁ and n₂ are refractive indices of two media, θ₁ and θ₂ are angles of incidence and refraction. Predicts the bending of light at an interface.
Lens Formula: 1/v - 1/u = 1/f
v is image distance, u is object distance, f is focal length of the lens. Similar to mirror formula but with a sign change. Used for lens image calculations.
Power of a Lens (P) = 1/f
f is focal length in meters. P is measured in diopters (D). Positive for convex lenses, negative for concave. Indicates lens strength.
Focal Length (f) = R/2
R is radius of curvature of a spherical mirror. Relates mirror's curvature to its focusing ability. Only valid for small apertures.
Critical Angle (θc) = sin⁻¹(n₂/n₁)
n₁ is refractive index of denser medium, n₂ is rarer medium. Angle beyond which total internal reflection occurs. Important for optical fibers.
Total Magnification for Two Lenses: m = m₁ × m₂
m₁ and m₂ are magnifications of individual lenses. Used when two lenses are combined. Multiplicative property of magnification.
Combined Power of Lenses: P = P₁ + P₂
P₁ and P₂ are powers of individual lenses. Algebraic sum gives total power. Useful for correcting vision with multiple lenses.
Equations
Laws of Reflection: i = r
i is angle of incidence, r is angle of reflection. Both angles are measured from the normal. Fundamental to all mirror problems.
Real Image Formation by Concave Mirror: u > f
u is object distance, f is focal length. Condition for real image formation. Real images are inverted and can be projected.
Virtual Image Formation by Convex Mirror: Always
Convex mirrors always produce virtual, erect, and diminished images. Used in rear-view mirrors for wider field of view.
Lens Maker’s Formula: 1/f = (n-1)(1/R₁ - 1/R₂)
n is refractive index of lens material, R₁ and R₂ are radii of curvature of lens surfaces. Derives focal length from lens geometry.
Linear Magnification for Lenses: m = v/u
v is image distance, u is object distance. Positive m indicates erect image, negative for inverted. Relates image size to object size.
Dispersion Formula: n = A + B/λ²
A and B are material constants, λ is wavelength. Explains separation of light into colors by prism due to wavelength-dependent n.
Power of Combination of Lenses: P_eq = P₁ + P₂ - dP₁P₂
d is distance between lenses. For thin lenses in contact, d=0 simplifies to P_eq = P₁ + P₂. Calculates effective power of lens systems.
Apparent Depth: Real Depth / n
n is refractive index of medium. Explains why objects in water appear shallower. Used in fish-eye view calculations.
Critical Angle Condition: sinθc = n₂/n₁
n₁ > n₂ for total internal reflection. Defines minimum angle for light to be totally reflected back into denser medium.
Focal Length of Concave Lens: Negative
By convention, concave lenses have negative focal lengths. Indicates diverging nature. Important for sign conventions in calculations.
Explore the versatile world of carbon, its allotropes, and the vast array of compounds it forms, including hydrocarbons and their derivatives, in this comprehensive chapter.
Life Processes explores the essential functions that sustain living organisms, including nutrition, respiration, transportation, and excretion.
Explore how organisms respond to stimuli and maintain homeostasis through the nervous and endocrine systems in the chapter on Control and Coordination.
This chapter explores the various methods of reproduction in organisms, including asexual and sexual reproduction, and the importance of reproduction in maintaining species continuity.
Explore the fascinating world of heredity, understanding how traits are passed from parents to offspring through genes and chromosomes.
