Unit 12 GEOMETRICAL OPTICS FBISE Class 10 Physics

Exploring Important Concepts in Chapter 12 - Geometrical Optics

Demystifying Geometrical Optics: Key Concepts for Class 10 Physics

CHAPTER 12: GEOMETRICAL OPTICS

You may find this chapter to be the most complicated because it deals exclusively with mirrors, lenses, and arrows. Because of the simple language in these notes, it would become simple.

Let's examine the lessons that this chapter should teach us.

Utilize Spherical Mirror Formula in Drive
List three applications for the spherical mirror.

Which laws of refraction are there?

Describe and demonstrate the key angle.

What is the entirety of the introspection? Write down its terms. Are you aware?

Before light rays enter the eye, a concave lens spreads them out to focus them on the retina and produce a sharp image.- Factmonster

Content: Theory, Exercise Solution, Numerical Problems 

UNIT 12 GEOMETRICAL OPTICS

CONCEPTUAL QUESTIONS

Question#1;

When you look at the front side of polished spoon, your image is inverted and from back of spoon, your image is erect. Explain why?

Answer;

Because the front Side of polished spoon behaves like a

Concave mirror while the back side of Spoon behaves like a

Convex mirror.

Explanation:

E a The front (concave) side of the spoon behaves as

Concave mirror and we know that' Concave mirror forms

inverted real image. The back (convex) side of the spoon

behaves as a Convex mirror and we know that Convex

mirror farms exact Virtual image.

Question 2;

Which mirror is used by girls for make up and why?

Answer;

Concave mirror is used by girls for make up because it forms magnified and upright image.

Explanation:

When the mirror is placed very near to that your face (object) lies

inside its focal length then exact and magnified image is formed

which helps you to see the details of your face and apply a Sharp

make up on Lit!

Question3;

Why are large convex mirrors fixed at blind turns of mountains?

Answer;

Large Convex mirrors are fixed at blind turns. of mountains to help drivers to See vehicles Coming from the other side.

Explanation:

An Image farmed in a Convex mirror is Smaller. When image the mirror Smaller, more images Can fit onto So a Convex mirror provides a larger field of view and helps the driver to See a larger area of the opposite sides. So in this way chances of accident Can be reduced.

Question4;

Which mirrors are used for rear view of vehicles and why?

Answer;

Convex mirrors are used for rear view of Vehicles because they

enable the driver to See a wide area of the road behind the Cax.

Explanation:

Convex mirrors form Smaller image: when image Is Smaller, more

images can fit anto the mirror, So a Convex mirror provides a

larger field of View and helps the driver to See a larger area of the

opposite side.

Question5;

If a person is walking in pool, why do his legs appear shorter in water?

Answer;

because of refraction of light.

Explanation:

When a ray of light enters from water to air, it is refracted away from the normal. The rays Coming from the legs appears to be slightly above the actual position. Therefore, the legs of the person appear Shorter in water.

Question 6;

Why do diamonds sparkle brightly?

Answer;

Diamands Sparkle brightly because of Hussle factors; reflection,

total internal reflection and dispersion. 

Explanation:

 Reflection: when light hits Surface of diamond, it reflects and

Create the appearance of a Sparkle.

 Total internal reflection: When light enters the

diamond it reflects multiple times in the diamond

because of total internal reflection and diamands

sparkle brightly."

 Dispersion: To Some extent diamond behaves like a

prism and disperse the light. So we can see Seven

Colors and diamonds sparkle brightly .w e r;

Question7;

When white light passes through a prism, it disperses into its seven colours. Why does dispersion take place in prism?

Answer;

when white light passes through a prism, it disperses into its

Seven Colours and it is called dispersion. Explanation:

white light is made up of Seven bands of Color's each having

different wavelengths upon passing through a prism, each of the

Colours travels at different speeds and hence has different angles

of refraction leading to the splitting of the light i;e dispersion.

Example: Red Color deviates least and is formed at the upper part of

the spectrum and Violet Color deviates more and is formed. at the

bottom. of the spectrum.

Question 8;

Magnifying glass can burn the paper. How is it possible?

Answer;

Magnifying glass is a Convex lens. As we know that Canvex lens

Converges all the light rays falling on it to a Single paint ie its

focus. So when light rays Converge at a point, the intensity of light

increases and the heat! all Concentrated on this point and it will

start burning.

Question9;

Your grandfather uses spectacles to read newspaper. You see through the spectacles and you observe that objects behind it were inverted. Why was it so observed?

Answer;

A Convex lens is used in the spectacles to read newspaper.

Therefore, the image formed byinverted.

Explanation:

When your grandfather reads the newspaper his eyes lie in the

focal length of the lens, so the image of newspaper is exect and

enlarged. But when you see from his glass standing behind him,

you are out of the focal length of the Convex lens, So the Image

of newspaper is inverted. That is the reason when we see through

the spectacles, You observe the objects behind the lens are

inverted.

Question 10;

Under what condition, is a convex lens nearly act as diverging lens?

Answer;

A Convex lens can behave as a diverging lens when it is placed in

a medium whose refractive index is greater than the

refractiveindex of the material of the lens. Example:

A Convex lens of glass (n=1·5) behave as a diverging lens when

immersed in Carbon disulphide of higher refractive index (n=1.6).

Condition 2: When an object is placed inside the focal length

Convex lens, the do not Converge to rays of a the opposite Side

of the lens, in this case Convex lens acts as diverging lens.

Here are conceptual questions with solutions for Chapter 12: Geometrical Optics:

Define optics and explain its branches.

Question: What is optics, and what are its main branches?

Solution: Optics is the branch of physics that deals with the behavior and properties of light, including its interactions with matter and its propagation. Its main branches include:

Geometrical optics: Deals with light propagation in terms of rays and how they interact with surfaces and objects.

Physical optics: Focuses on the wave nature of light and phenomena such as diffraction and interference.

• Describe the behavior of light as it passes through different mediums.

Question: How does light behave when it passes through different mediums?

Solution: Light may refract (bend) or reflect when it passes from one medium to another. The amount of bending depends on the refractive indices of the two mediums.

• Explain the laws of reflection and refraction of light.

Question: What are the laws governing the reflection and refraction of light?

Solution:

Laws of reflection: The angle of incidence is equal to the angle of reflection.

Laws of refraction (Snell's Law): The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for a given pair of media.

Discuss the difference between real and virtual images.

Question: How do real and virtual images differ?

Solution:

Real images are formed when actual light rays converge at a point, and they can be projected onto a screen.

Virtual images are formed by the apparent intersection of light rays when traced backward, and they cannot be projected onto a screen.

• Describe the formation of images by plane mirrors and convex/ concave lenses.

Question: How are images formed by plane mirrors and lenses?

Solution:

Plane mirrors: Form virtual, upright, and laterally inverted images of objects.

Convex lenses: Can form both real and virtual images, depending on the object's position relative to the focal point.

Concave lenses: Always produce virtual, upright, and reduced images.

• Explain the concept of focal length and its significance in optics.

Question: What is focal length, and why is it important in optics?

Solution: Focal length is the distance between the center of a lens or curved mirror and its focal point. It determines the size and position of images formed by optical devices.

• Discuss the working principle of the human eye.

Question: How does the human eye function to create vision?

Solution:

Light enters the eye through the cornea and is refracted by the lens to form an inverted image on the retina. Photoreceptor cells in the retina convert light into electrical signals, which are transmitted to the brain via the optic nerve for interpretation.

• Explain the concept of optical instruments such as microscopes and telescopes.

Question: How do optical instruments like microscopes and telescopes work?

Solution:

Microscopes magnify small objects by using lenses to produce enlarged images.

Telescopes gather and magnify distant light, allowing us to see celestial objects more clearly.

• Describe the phenomenon of dispersion of light and its applications.

Question: What is dispersion of light, and how is it applied?

Solution: Dispersion occurs when white light is separated into its component colors (wavelengths) as it passes through a prism. Applications include:

Rainbow formation

Spectroscopy in scientific research