Elite Edusphere Institute

Here is every "Must-Know" concept of Light , compressed into one post. 💡📖

1️⃣ THE BASICS
Light: An electromagnetic wave. It travels in a straight line (Rectilinear propagation).

Speed: 3×10⁸m/s in vacuum.

2️⃣ REFLECTION (MIRRORS)
Law: Angle of incidence (i) is ALWAYS equal to the angle of reflection (r).

Concave Mirror: Converging. Used in torches, shaving mirrors, and by dentists.

Convex Mirror: Diverging. Always gives a diminished, erect image. Used as rear-view mirrors in vehicles.

Mirror Formula:

1/f= 1/v + 1/u


3️⃣ REFRACTION (BENDING)
The Cause: Light changes speed when it enters a different medium (e.g., Air to Glass).

Snell’s Law: The ratio "sini/sinr" is constant for a given pair of media (Refractive Index).

Refractive Index (n):

n= c/v


(Speed of light in air / Speed in medium).

4️⃣ LENSES (THE POWER)
Convex Lens: Converging (Think: Magnifying glass).

Concave Lens: Diverging (Think: Correcting Myopia).

Lens Formula:

1/f= 1/v-1/u


Power (P): Measured in Dioptres (D).

P= 1/f (in meters)


5️⃣ DISPERSION (THE PRISM)
Action: White light enters a prism and splits into VIBGYOR (Violet bends the most, Red the least).

Atmospheric Refraction: Why stars twinkle and why we see the sun 2 minutes early!

🧪 MASTER SPECIALIST TIPS:
Sign Convention: Always treat u (object distance) as negative (−).

Magnification (m): If m is negative, the image is Real.
If m is positive, it’s Virtual.

Units: Always convert Focal Length (f) to meters before calculating Power.

SAVE THIS POST for your revision.
SHARE with a classmate who is struggling with Ray Diagrams.

Elite Edusphere Institute
Concept Engineering by EEI.

📐 Trigonometry Made Simple – Class 10.
This is your complete mini-map of the chapter.

Here’s what you really need to understand:

1️⃣ Right Triangle Basics – Every ratio starts here.
Hypotenuse, Opposite, Adjacent → the foundation of all trigonometry.

2️⃣ Trigonometric Ratios – sinθ, cosθ, tanθ
Know what they mean, not just memorize.

3️⃣ Reciprocal Ratios – cosecθ, secθ, cotθ
They are just flips of the main ratios.

4️⃣ Fundamental Identity – sin²θ + cos²θ = 1
Every other formula comes from this.

5️⃣ Standard Angles – 0°, 30°, 45°, 60°, 90°
Remember these visually, they save time in exams.

6️⃣ Complementary Angles – sin(90° − θ) = cosθ, tan(90° − θ) = cotθ
Patterns you can actually see instead of cramming.

7️⃣ Quick Mini Map – Everything connected in one glance
Ratios → Reciprocal → Identity → Angles → Complementary.

💡 Trigonometry is easier when you understand connections, not just memorize formulas.

Save this carousel. Swipe back anytime. Revision made easy.

EEI – Making Maths Visual, Simple, and Student-Friendly.