IB SL PHYSICS Review Sheet-Option A-Sight and Wave Phenomena A1. Vision – Parts of eye  Depth of vision: Requires two lenses/eyes and brain puts the 2 images together to judge depth….more important for nearby objects than those further away, ability to see in 3D.  Accommodation: Is accomplished in the eye by the cillary muscles flexing and changing the shape of the lens of the eye and thus changing the focal point of the eye – thus enabling the eye to focus and distinguish objects at different distances. (changing focal length enables image to fall on the retina of the eye)  Near Point-The closest point to the eye at which an object can be focused without excessive strain. The near point of a normal human eye is about 25 cm. (D=25cm)  Far Point-Furthest distance at which objects can be focused clearly. For normal human eye the distance to the far point is assumed to be infinity.  Rods: Cells are useful at night and for other poor lighting conditions because they are more sensitive to light of low intensity, see in black and white, scotopic vision.  Cones-Cells are used mainly in normal lighting conditions, 3 cones, red, green blue, used in color vision, photopic vision. Density along retina: cones in the center, rods on the peripheral of the retina.  Photopic vision: (alphabetical p before s photopic/scotopic and cones before rods) Uses cones, used in high intensity light, does distinguish colors, sees detail – (reading small letters) CCD cones color detail - cones for color  Scotopic vision: Uses rods, used in low intensity light does not distinguish between colors (only black and white), does not see detail, detects motion – rods for night vision and motion.  Color Mixing: 3 primary colors Red, Green, and Blue, 3 secondary colors yellow, magenta, and cyan are the result of mixing 2 primary colors, White light results from mixing all 3. Lighting effects of light and dark in terms of size, height, massiveness, 3d effects. A2. Standing Waves: The superposition of two identical waves traveling in opposite directions. Formed when a wave hits a boundary and reflects back it comes out 180 degrees out of phase. Two fixed ends: Must be nodes at each end, the possible frequencies are given below. Standing Wave Progressive wave  Energy Transfer No transfer, energy confined to space the wave occupies Energy transferred along with wave Amplitude Not all points have the same amplitude All points have the same amplitude Phase All points between nodes are in phase Points are not in phase NODES and ANTINODES: Nodes destructive interference waves cancel each other out continually, amplitude a minimum, antinodes, interference chances from maximum positive, to zero, to maximum negative, amplitude a maximum.  STRINGS: Two fixed ends, and one fixed and one free end.  PIPES: Two open ends, one open end and one closed end. Two open ends (pipe) (antinodes at ends) Two fixed ends (rope or string) (nodes at ends)  A3. All travel at the same speed Wavelength x frequency same for all harmonics Standing waves have different amplitudes at different points and do not transfer energy. Traveling waves transfer energy and the amplitude is the same at any point on the wave. Fundamental wave has lowest (smallest) frequency and biggest wavelength, second harmonic is twice the frequency and ½ the wavelength, third harmonic is 3x the frequency and 1/3 rd the wavelength. DOPPLER EFFECT: The apparent change of frequency that is detected when there is relative motion between a source and a receiver of waves. Approximation formula useful when v << c (note c is not necessarily 3 x 108) { { } } A4. SINGLE SLIT DIFFRACTION: When light passes through a slit it diffracts on a screen and the following pattern is observed. A5. RESOLUTION RAYLEIGH CRITERIA: Two point sources are just resolved if the first minimum of the diffraction pattern of one occurs at the same angle as the central maximum of the other, where b is the diameter of the lens (this formula is for a circular aperture/opening). Often used in problems with =s/r. Increasing resolution means making the angle  smaller. You use =/b for a slit and =1.22/b for a circular opening.  A6. POLARIZATION: Polarized light is light that oscillating in only one plane. The electric field, magnetic field and direction of propagation are all mutually perpendicular. Ways to polarize light 1) by reflection 2) a polarizing filter called a Polaroid 3) by selective absorption  BREWSTER ANGLE: Angle of incidence at which the reflected light is polarized horizontally and the refracted beam in partially polarized.   POLARIZER: A special filter that can convert unpolarized light into polarized light.  MALUS LAW: The angle between the oscillations and the plane in which the polarizer will transmit all of the waves. The intensity varies according to Malus’ Law  OPTICALLY ACTIVE: A substance which rotates the plane of polarization of light waves passing through it. Uses: o o o Stress Analysis Solution Concentration LED crystal displays