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Physics fundamentally investigates the interactions between the building blocks of our universe. This topic, which includes a wide range of sub-fields from nuclear physics to quantum physics, is a crucial component of the syllabus. Physics is associated with numerical difficulties. However, physics may be a much more engaging subject. The limits of physics are not clearly defined, and it interacts with many interdisciplinary fields of study, including quantum chemistry and biophysics. The underlying mechanisms investigated by other sciences are frequently explained by new concepts in physics, and this opens up new directions for investigation in these and other academic fields like mathematics and philosophy. It is the goal of physics to identify the basic elements and interactions that make up our universe.The majority of physics is based on these standard formulas.
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| Table of Content |
KeyTerms: Concave mirror, Convex mirror, Lens, Focal length, Electric current, Power
Image formation by concave mirror
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Concave mirrors can create both physical and digital pictures. A virtual, enlarged picture of the object is produced when the concave mirror is put very close to it. As the distance between the object and the mirror increases, the size of the image decreases and real images are produced.
Image formation by convex mirror
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Images created by convex mirrors are always virtual. This is so because the convex mirror's focal point and curvature center are fictitious positions that are impossible to approach. A screen cannot be projected since the picture is created inside the mirror.
Mirror formula
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The mirror formula can be written as:
\(\frac{1}{f} = \frac{1}{v} + \frac{1}{u}\)where,
f = focal length
v = image distance
u = object distance
Magnification
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In relation to the size of the original object, the magnified image created by a sphere mirror is said to have a magnification factor of 1. It is measured in millimeters and represents the proportion of the image height to the actual object height.
M = – v/u
where,
v = image distance
u = object distance
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| Relevant Concepts | ||
|---|---|---|
| Current Electricity | Power of a lens | Biconvex lens |
| Lens maker’s formula | Compound microscope | Telescope |
Lens formula
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A lens is a piece of glass that either directs light rays away from one concentrated point or concentrates them at another. With the aid of dispersion, it performs the converging or diverging. A compound lens is made up of many lenses, as opposed to a simple lens, which is made of a transparent substance.
\(\frac{1}{f} = \frac{1}{v} - \frac{1}{u}\)
where,
f = focal length
v = image distance
u = object distance
Speed of light in air/vacuum is 3 × 108¸ m s-1
Focal length
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Focal length is defined as the distance between the pole (the point closest to the lens) of a convex lens or the center of a concave lens to the point where the parallel light rays passing through the lens meet or appear to meet after refraction.
It is denoted by f,
f = R/2
where,
R is the radius
Linear magnification
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Linear magnification refers to the ratio of the size of the image to the size of the object. It is typically represented by the symbol "m" and is calculated as the ratio of the size of the image (I) to the size of the object (O)
That is,
m = I / O
where,
m = the linear magnification
I = the size of the image
O = the size of the object
Electric current
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Electric current is the flow of electric charge through a material. It is typically measured in amperes (A) and is the rate at which electric charge flows through a circuit.
I = Q/t
SI unit of electric current is ampere(A).
Electric Potential
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Electric potential is defined as work done per unit charge, that is
V= W/q
SI unit of electric potential is volt(V)
Electric Power
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It is defined as the amount of electric work done in one second.
SI unit of electric power is watt
P = VI = I2R = V2/R
where,
P = power
V = potential difference in the circuit.
I = electric current.
Things to remember
- The laws of reflection state that the angle of incidence is equal to the angle of reflection, and the incident ray, reflected ray, and the normal to the reflecting surface all lie in the same plane.
- Concave mirrors are curved inward and are used to diverge light and can form virtual, diminished and inverted images.
- Convex mirrors are curved outward and are used to converge light and can form smaller, virtual and erect images.
- The law of reflection states that when a ray of light strikes a reflecting surface, the angle of incidence is equal to the angle of reflection
- Resistance is a measure of how much a material opposes the flow of electric current. It is measured in ohms (Ω).
- A lens is a piece of glass that either directs light rays away from one concentrated point or concentrates them at another.
Sample questions
Ques. Mention lens formula (2 marks)
Ans.
\(\frac{1}{f} = \frac{1}{v} - \frac{1}{u}\)where,
f = focal length
v = image distance
u = object distance
Ques. Mention formula for electric current. (2 marks)
Ans. Electric current is the flow of electric charge through a material. It is typically measured in amperes (A) and is the rate at which electric charge flows through a circuit.
I = Q/t
SI unit of electric current is ampere(A).
Ques. A ray of light is incident at an angle of 30 degrees on a plane mirror. What is the angle of reflection? (1 mark)
Ans. According to the law of reflection, the angle of incidence is equal to the angle of reflection. Therefore, the angle of reflection is also 30 degrees.
Ques. An object is placed 15 cm in front of a concave mirror. The image is formed at a distance of 10 cm from the mirror. What is the nature and the size of the image? (1 mark)
Ans. Since the image is formed behind the mirror and the object distance is less than the focal length, the image is virtual, erect and smaller in size than the object.
Ques. A current of 10 amperes flows through a wire for 2 hours. How much electric energy is transferred during this time? (5 marks)
Ans. Electric energy (E) is equal to current (I) multiplied by potential difference (V) multiplied by time (t).
Since the potential difference is not given,
use Ohm's law which states that V = IR.
In this case,
E = I x V x t
= 10 x (10 x R) x (2 x 3600)
= (10 x R) x 72,000.
= 7200
Ques. If a current of 5 A flows through a resistor of 20 ohms, what is the potential difference across the resistor? (3 marks)
Ans. According to Ohm's law, the potential difference (V) across a resistor is equal to the current (I) flowing through it multiplied by the resistance (R).
Therefore, V = IR.
In this case,
V = 5 x 20
= 100 V
Ques. A current of 1 A flows through a wire for 1 hour. The wire has a resistance of 2 ohms. What is the power consumed by the wire? (3 marks)
Ans. Power is equal to current squared multiplied by resistance.
Therefore,
P = I2 x R.
In this case,
P = 12 x 2
= 2 W.
Ques. If a charge of 2 Coulombs is moved through a potential difference of 10 volts, what is the work done? (3 marks)
Ans. Work done (W) is equal to the charge (Q) multiplied by the potential difference (V). Therefore,
W = Q x V. I
n this case,
W = 2 x 10
= 20 Joules
Ques. A current of 2 amperes flows through a resistor of 10 ohms. What is the potential difference across the resistor? (3 marks)
Ans. According to Ohm's law, the potential difference (V) across a resistor is equal to the current (I) flowing through it multiplied by the resistance (R).
Therefore, V = IR.
In this case,
V = 2 x 10
= 20 V
Ques. A current of 5 amperes flows through a wire with a resistance of 20 ohms. What is the power consumed by the wire? (3 marks)
Ans. Power (P) is equal to current (I) multiplied by potential difference (V). We can use Ohm's law to find the potential difference V = IR.
In this case,
P = I x V
= 5 x (5 x 20)
= 500 W
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