optics gr 10

What is a real image?

A real image is formed when reflected or refracted light rays actually converge at a point. It can be projected onto a screen and is typically inverted.

What is a virtual image?

A virtual image is formed when reflected or refracted light rays appear to diverge from a point. It cannot be projected onto a screen and is typically upright.

Describe the kinds of images that can be formed by plane mirrors.

Plane mirrors form images that are upright, virtual, the same size as the object, and located the same distance behind the mirror.

What type of mirror produces only diverging rays?

A convex (diverging) mirror produces only diverging rays.

What type of mirror can produce both converging and diverging rays?

A concave (converging) mirror can produce both converging rays (for real images formed outside the focal point) and diverging rays (when forming virtual images, i.e., when the object is inside the focal point).

What kind of mirror would you use to view a large, spread-out area in a small mirror?

A convex mirror would be used because it always forms smaller, virtual, upright images, which increases the field of view.

Compare the shapes of convex and concave mirrors.

Both convex and concave mirrors are typically sections of a sphere. Concave mirrors curve inward, like the inside of a spoon, causing parallel light rays to converge. Convex mirrors curve outward, like the back of a spoon, causing parallel light rays to diverge.

What kind of images do convex mirrors form?

Convex mirrors always form images that are virtual, upright, and smaller than the object.

What are three uses for convex mirrors?

Convex mirrors are commonly used as passenger-side car mirrors, security mirrors in stores, and for blind spot detection because they provide a wider field of view.

Describe the light rays reflecting off a concave mirror when a lighted object is placed at its focal point (F).

When an object is placed at the focal point (F) of a concave mirror, the light rays reflecting off the mirror will be parallel to the principal axis. No image is formed.

When is light travelling at its fastest?

Light travels at its fastest in a vacuum, where its speed (c) is approximately 3.00 \times 10^8 \text{ m/s}.

What is dispersion?

Dispersion is the phenomenon where white light separates into its constituent colors (spectrum) when it passes through a medium, due to different wavelengths bending at slightly different angles.

Under what conditions can you slow down light and then speed it up again?

Light slows down when it passes from a vacuum (or a medium with a lower index of refraction) into a denser optical medium (higher index of refraction). It speeds up again when it exits the denser medium and returns to a vacuum or a medium with a lower index of refraction.

Through which medium does light pass more quickly, one with a refractive index of 1.1 or one with a refractive index of 2.2?

Light passes more quickly through the medium with a refractive index of 1.1. A lower index of refraction indicates a faster speed of light in that medium (n = c/v).

What type of lens produces a real image?

A converging (convex) lens can produce a real image, specifically when the object is placed outside its focal point.

What type of lens produces a virtual image?

Both converging (convex) lenses (when the object is inside the focal point) and diverging (concave) lenses (always) can produce virtual images.

What is one use for a diverging lens?

One common use for a diverging (concave) lens is to correct myopia (nearsightedness).

How is the focal point (F) of a mirror different from the vertex (V)?

The vertex (V) is the point where the principal axis intersects the mirror surface. The focal point (F) is a specific point on the principal axis where parallel incident rays converge after reflection (concave) or appear to diverge from (convex). F is a distance along the principal axis from V (f = R/2).

Which substance refracts light more, water or glass? Explain why.

Glass generally refracts light more than water. This is because glass typically has a higher index of refraction (n{glass} > n{water}), meaning light slows down more significantly in glass, causing a greater change in direction (bending) as described by Snell's Law.

What is the speed of light?

The speed of light in a vacuum is approximately 3.00 \times 10^8 \text{ m/s}.

Define critical angle.

The critical angle (\theta_c) is the angle of incidence in a denser medium for which the angle of refraction in the less dense medium is 90^\circ. Beyond this angle, total internal reflection occurs.

Which will be larger: the critical angle at an air-glass interface or the critical angle at a water-glass interface? Explain.

The critical angle at a water-glass interface will be larger. The critical angle is defined by \sin \thetac = \frac{n2}{n1} . Since the difference in refractive indices between glass (n \approx 1.5) and water (n \approx 1.33) is smaller than the difference between glass and air (n \approx 1.00), the ratio n2/n_1 is larger for the water-glass interface (when light travels from glass to water), resulting in a larger critical angle.

True or false: The normal is drawn at a 90^\circ angle to the mirror or lens.

True. The normal is always perpendicular (at a 90^\circ angle) to the surface at the point of incidence.

True or false: When light is reflected from a curved mirror, the angle of incidence is twice the angle of reflection.

False. According to the Law of Reflection, the angle of incidence is equal to the angle of reflection (\thetai = \thetar).

Label the Electromagnetic Spectrum, from longest wavelength to shortest wavelength.

From longest wavelength (lowest frequency/energy) to shortest wavelength (highest frequency/energy):

• Radio waves (Long Wave Side)
• Microwaves
• Infrared light
• Visible light
• Ultraviolet light
• X-rays
• Gamma rays (Short Wave Side)

True or false: As wavelength increases, frequency increases in the electromagnetic spectrum.

False. As wavelength increases, frequency decreases (assuming constant wave speed c = \lambda f). Wavelength and frequency are inversely proportional.

What are the characteristics of an image formed by a concave mirror when the object is Beyond its Center of Curvature (C)?

The image will be smaller, inverted, and real, located between F and C.

What are the characteristics of an image formed by a concave mirror when the object is At its Center of Curvature (C)?

The image will be the same size as the object, inverted, and real, located at C.

What are the characteristics of an image formed by a concave mirror when the object is Between its Center of Curvature (C) and Focal Point (F)?

The image will be bigger, inverted, and real, located beyond C.

What are the characteristics of an image formed by a concave mirror when the object is At its Focal Point (F)?

When an object is placed at the focal point (F) of a concave mirror, no image is formed, as the reflected rays are parallel and do not converge or diverge.

What are the characteristics of an image formed by a concave mirror when the object is Inside its Focal Point (F)?

The image will be bigger, upright, and virtual, located behind the mirror.

What are the characteristics of an image formed by a convex mirror?

A convex mirror always forms an image that is virtual, upright, and smaller than the object, located behind the mirror.

What are the characteristics of an image formed by a converging (convex) lens when the object is Outside its Focal Point (F)?

The image will be real and inverted. Its size and exact location depend on the object's distance relative to F and 2F.

What are the characteristics of an image formed by a converging (convex) lens when the object is Inside its Focal Point (F)?

The image will be virtual, upright, and bigger than the object, located on the same side of the lens as the object.

What are the characteristics of an image formed by a diverging (concave) lens?

A diverging (concave) lens always forms an image that is virtual, upright, and smaller than the object, located on the same side of the lens as the object.