RRB JE Science 2025 Preparation: High-Weightage Topics & Most Expected Questions for CBT 1

If you’re preparing for competitive exams like RRB JE, SSC, State-Level Engineering Exams, or other technical tests, this session covers high-frequency Science topics with conceptual clarity and exam-oriented practice. Below is a structured breakdown of important concepts along with formulas and expected question areas.

1. Refraction of Light & Refractive Index (Very Important)

What is Refraction?

Refraction is the bending of light when it passes from one medium to another due to a change in speed.

Refractive Index Formula:
n = c / v

Where:
n = Refractive index
c = Speed of light in vacuum (3 × 10^8 m/s)
v = Speed of light in medium

Example:
If speed in glass = 2 × 10^8 m/s

n = (3 × 10^8) / (2 × 10^8)
n = 1.5

Relative Refractive Index (Snell’s Law):
n = sin i / sin r

Where:
i = angle of incidence
r = angle of refraction

Critical Angle Formula:
sin C = 1 / n

If n = 1.5

sin C = 1 / 1.5
sin C = 0.67

2. Human Heart – Important Biology Facts

Thickest muscular wall: Left Ventricle (pumps blood to the whole body)
Natural pacemaker: SA Node (Sinoatrial Node)
Valve between the right atrium and the right ventricle: Tricuspid valve

3. Cathode Rays

Cathode rays are streams of negatively charged particles (electrons).
Electron was discovered by J.J. Thomson.

4. Electrical Conductance & Resistance (High Probability Topic)

Conductance Formula:
G = 1 / R

Unit of conductance: Siemens (S)

Important Relationships:
G ∝ A
G ∝ 1 / L
G ∝ 1 / ρ

Where:
A = Area
L = Length
ρ = Resistivity

Temperature Effect in Metals:
Temperature increases → Resistance increases
Resistance increases → Conductance decreases

Parallel Conductance:
G_total = G1 + G2

5. Pressure (Important Numerical Topic)

Pressure Formula:
P = F / A

If mass is given:
F = m g

Example:
m = 50 kg
g = 10 m/s^2
A = 0.5 m^2

F = 50 × 10
F = 500 N

P = 500 / 0.5
P = 1000 Pa

Liquid Pressure Formula:
P = h ρ g

Where:
h = depth
ρ = density
g = acceleration due to gravity

Important Concept:
For the same force, a smaller area produces greater pressure.

6. Most Reactive Metal

Among common options: Calcium (based on reactivity series).

7. Longest & Smallest Bones

Longest and strongest bone: Femur
Smallest bone: Stapes (ear)

8. Sound & Waves

Sound travels fastest in solids.
The speed of sound increases with temperature.
Torque is not a scalar quantity; it is a vector quantity.

9. Vitamins

Vitamin B complex consists of 8 vitamins.
Deficiency of Vitamin B1 causes Beriberi.

10. Convex Lens – Image Formation Cases

A convex lens is a converging lens.

Cases:

1. Object at infinity
   Image at F
   Real, inverted, highly diminished
   
   

2. Object beyond 2F
   Image between F and 2F
   Real, inverted, diminished
   
   

3. Object at 2F
   Image at 2F
   Real, inverted, same size
   
   

4. Object between F and 2F
   Image beyond 2F
   Real, inverted, enlarged
   
   

5. Object between F and optical center (O)
   Image behind the lens
   Virtual, erect, magnified

6. Chemistry Quick Facts
   
   

Copper mineral: Copper glance

Symbol of gold: Au
Sweet-smelling compounds: Esters
Gas used for anesthesia: Nitrous oxide
Helium is used in balloons because it is lighter than air and non-flammable.

12. Organic Chemistry Concept

Unsaturated compounds contain double or triple bonds.

Examples:
Alkene: C = C
Alkyne: C ≡ C

Butane is not unsaturated because it contains only single bonds.

13. Brain & Emotions

The limbic system controls emotion, memory, and motivation.

14. Pascal’s Law

Application: Hydraulic systems

15. Digestion

HCl is released in the stomach.
Salivary amylase breaks starch into sugar.

Final Exam Strategy Tips

• Revise formulas daily.
• Practice numericals from Pressure, Refraction, and Conductance.
• Memorize important biology facts (heart, bones, vitamins, brain).
• Revise the convex lens image cases thoroughly.
• Solve previous year questions regularly for accuracy and speed.