What is light?
Light is an electromagnetic wave that travels through a vacuum at a speed of approximately \(3.0 \times 10^8 \, \text{m/s}\).
What is the speed of light in a vacuum?
\(c = 3.0 \times 10^8 \, \text{m/s}\)
What is the law of reflection?
The angle of incidence is equal to the angle of reflection: \( \theta_i = \theta_r \)
What type of image does a plane mirror form?
A virtual, upright, and laterally inverted image of the same size as the object.
What is refraction?
The bending of light as it passes from one medium to another due to a change in speed.
What is the refractive index formula?
\( n = \frac{c}{v} \), where \(c\) is the speed of light in vacuum and \(v\) is the speed in the medium.
What is Snell’s Law?
\( n_1 \sin \theta_1 = n_2 \sin \theta_2 \)
What is a real image?
An image formed when light rays actually converge and can be projected on a screen.
What is a virtual image?
An image formed when light rays appear to diverge; it cannot be projected on a screen.
How is the image formed by a convex mirror?
Virtual, upright, and diminished image behind the mirror.
How is the image formed by a concave mirror (object beyond C)?
Real, inverted, and diminished image between C and F.
Mirror formula
\( \frac{1}{f} = \frac{1}{u} + \frac{1}{v} \)
What is the magnification formula for mirrors?
\( M = \frac{h_i}{h_o} = \frac{-v}{u} \)
What is a converging lens?
A convex lens that focuses parallel light rays to a point.
What is a diverging lens?
A concave lens that spreads out parallel light rays.
Lens formula
\( \frac{1}{f} = \frac{1}{v} - \frac{1}{u} \)
Magnification formula for lenses
\( M = \frac{h_i}{h_o} = \frac{v}{u} \)
What is the power of a lens?
\( P = \frac{100}{f(\text{cm})} = \frac{1}{f(\text{m})} \), unit is dioptre (D)
Sign convention for convex lens
Focal length and image distance are positive if image is real.
Image formed by convex lens when object is at 2F
Real, inverted, and same size image at 2F
Image formed by convex lens when object is between F and 2F
Real, inverted, and magnified image beyond 2F
Image formed by convex lens when object is at F
Image at infinity, highly magnified and real
Image formed by convex lens when object is between lens and F
Virtual, upright, and magnified image on the same side as the object
Image formed by concave lens regardless of object position
Virtual, upright, and diminished image on the same side as the object
What does the focal length of a lens depend on?
The curvature of the lens surfaces and the refractive index of the material
How do you calculate the refractive index using angle of incidence and refraction?
\( n = \frac{\sin i}{\sin r} \)
Critical angle formula
\( \sin C = \frac{1}{n} \) (from denser to rarer medium)
What is total internal reflection?
When the angle of incidence exceeds the critical angle, causing all light to reflect back into the denser medium
What is dispersion of light?
The separation of light into its component colors due to different refractive indices for different wavelengths
Color with shortest wavelength
Violet
Color with longest wavelength
Red
White light is a mixture of?
Seven colors: red, orange, yellow, green, blue, indigo, violet (ROYGBIV)
What is the unit of lens power?
Dioptre (D)
How is the power of combination of lenses calculated?
\( P = P_1 + P_2 + \cdots + P_n \)
Use of convex lens in daily life
Used in magnifying glasses, cameras, and the human eye (cornea and eye lens)
Use of concave lens in daily life
Used in peepholes and to correct short-sightedness (myopia)
Focal length of a plane mirror
Infinite
Which lens has a negative focal length?
Concave lens
Which lens has a positive focal length?
Convex lens
How does light behave when moving from air into glass?
It slows down and bends toward the normal
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