# Physics Formulas for Class 10

The physics formulas for class 10 are based on NCERT science textbook. These formulas are in tune with CBSE syllabus. You can download these formulas from the link given above. You may also like physics formulas for class 11 and 12.

## Formulas on Reflection of Light

### Laws of Reflection

1. Incident ray, reflected ray, and normal at the point of incidence lie in the same plane.
2. The angle of incidence is equal to the angle of reflection i.e., $\angle i=\angle r$.

### Reflection from a Plane Mirror

1. The image is virtual. The image and the object are equidistant from the mirror.
2. The object size is equal to the image size i.e., magnification is 1.

### Reflection from a Spherical Mirror

1. New cartesian sign convention (i) the distances are measured from the pole P (ii) the distances in the direction of incident ray are positive.
2. Focal length is equal to half of radius of curvature i.e., $f=R/2$.
3. The object distance $u$, image distance $v$ and focal length $f$ are related by the mirror formula: $$\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$$
4. The magnification is the ratio of image height to the object height and it is given by $$m=-\frac{v}{u}$$

## Formulas on Refraction of Light

### Refractive Index

$$\mu=\frac{\text{speed of light in vacuum}}{\text{speed of light in medium}}=\frac{c}{v}$$

### Laws of Refraction

1. Incident ray, refracted ray, and normal at the point of incidence lie in the same plane.
2. The angle of incidence is related to the angle of refraction by Snell's Law: $$\frac{\sin i}{\sin r}=\frac{\mu_2}{\mu_1}$$

### Lens Formula

The object distance $u$, image distance $v$ and focal length $f$ of a lens are related by the lens formula $$\frac{1}{v}-\frac{1}{u}=\frac{1}{f}$$ The magnification by a lens is given by $$m=\frac{v}{u}$$

### Power of a Lens

The power of a lens is related to its focal length by $$P={1}/{f}$$ The power $P$ in diopter if $f$ in metre.

## Electricity Formulas

### Electric Current

The electric current in a wire is equal to the charge flowing per unit time in it i.e., $$I=Q/t$$

### Potential Difference

The potential difference between two points is the work required to move a unit charge from one point to the other i.e., $$V=W/Q$$

### Resistance

The resistance of a wire of length $l$ and cross-sectional area $A$ is given by $$R=\rho l/A,$$ where $\rho$ is the resistivity of the wire material.

### Ohm's Law

The current through a wire of resistance $R$ connected to a source of potential $V$ is given by $$V=IR$$

### Resistors in Parallel

The equivalent resistance $R_\text{eq}$ of two resistors connected in parallel is given by $$\frac{1}{R_\text{eq}}=\frac{1}{R_1}+\frac{1}{R_2}$$

### Resistors in Series

The equivalent resistance $R_\text{eq}$ of two resistors connected in series is given by $$R_\text{eq}=R_1+R_2$$

### Electric Power

The electric power of a device of resistance $R$ connected to a source of voltage $V$ is given by $$P=V^2/R=I^2 R=IV$$

### Heating Effect

The heat generated in time $t$ is given by $$H=Pt=I^2 R t$$ See Books Dr HC Verma, Jitender Singh and Shraddhesh Chaturvedi