The region of the vertebrate eye, where the optic nerve passes out of the retina, is called the
(a) fovea
(b) iris
(c ) blind spot
(d) optic chaisma

Of the following statements , which are true for S_(N)2 reaction. (a) Tertiar alkyl halides reacts faster than secondary. (b) The absolute configuration of product is opposite to that of the reactant when an optically active substrate is used. (c) The used shows first order kinetics. (d) The rate of the reaction depends markedly on the nucleophilicity of the attacking reagent. (e) The mechanism is one step. (f) Carbocations are intermediate. (g) Rate prop [Alkyl][halides] (h) The rate of the reaction depends on the nature of the leaving group.

The phenomenon observed in some plants where in parts of the sexual apparatus is used for forming embryous without fertilisation is called (A) Parthenocarpy (B) Apomixis (C) Vegetative propagation (D) Sexual reproduction

Acceleration of particle moving along the x-axis varies according to the law a=-2v , where a is in m//s^(2) and v is in m//s . At the instant t=0 , the particle passes the origin with a velocity of 2 m//s moving in the positive x-direction. (a) Find its velocity v as function of time t. (b) Find its position x as function of time t. (c) Find its velocity v as function of its position coordinates. (d) find the maximum distance it can go away from the origin. (e) Will it reach the above-mentioned maximum distance?

In a p-n junction diode, the current I can be expressed as I= I_(0) "exp" ((eV)/(2k_(B)T)-1) where I_(0) is called the reverse saturation current, V is the voltage across the diode and is positive for forward bias and negative for reverse bias, and I is the current through the diode, k_(B) is the Boltzmann constant (8.6 xx 10^(–5) eV//K) and T is the absolute temperature. If for a given diode I_(0) = 5 xx 10^(-12) A and T = 300 K, then (a) What will be the forward current at a forward voltage of 0.6 V? (b) What will be the increase in the current if the voltage across the diode is increased to 0.7 V? (c) What is the dynamic resistance? (d) What will be the current if reverse bias voltage changes from 1 V to 2 V?

In a p-n junction diode, the current I can be expressed as I=I_(0)"exp"((eV)/(2k_(B)T)-1) where I_(0) is called the reverse saturation current, V is the voltage across the diode and is positive for forward bias and negative for reverse bias, and I is the current through the diode, k_(B) is the Boltzmann constant (8.6xx10^(-5)eV//K) and T is the absolute temperature. If for a given diode I_(0)=5xx10^(-12) A and T = 300 K, then (a) What will be the forward current at a forward voltage of 0.6 V ? (b) What will be the increase in the current if the voltage across the diode is increased to 0.7 V ? (c ) What is the dynamic resistance? (d) What will be the current if reverse bias voltage changes from 1 V to 2 V ?

Explain why : (a) a body with large reflectivity is a poor emitter (b) a brass tumbler feels much colder than a wooden tray on a chilly day (c) an optical pyrometer (for measuring high temperatures calibrated for an ideal black body radiation gives too low a value for the temperature of a red hot Iron plece in the open, but gives a correct value for the temperature when the same plece is in the fumace (d) the earth without its atmosphere would be inhospitably cold (e) heating systems based on circulation of steam are more efficient in warming a building than those based on circulation of hot water

Thin films, including soap bubbles and oil slicks, show patterns of alternating dark and bright regions resulting from interference among the reflected light waves. If two waves are in phase their crest and troughs will coincide. The interference will be constructive and the aplitude of the resultant wave will be greater than the amplitude of either constituent wave. if the two waves are out of phase, the crests of one wave will coincide with the troughs of the other wave. The interference will be destructive and the amplitude of the resultant wave will be less than that of either constituent wave. at the interface between two transparent media some light is reflected and some light is refracted. * When incident light, reaches the surface at point a, some of the light is reflected as ray R_(a) and and some is refracted following the path ab to the back of the film. *At point b some of the light is refracted out of the film and part is reflected back refracted out of the fiml as ray R_(c) . R_(a) and R_(c) are parallel. However, R_(c) has travelled the extra distance within the film of abc. if the angle of incidence is small then abc is approximately twice the film's thickness. if R_(a) and R_(c) are in phase they will undergo constructive interference and the region ac will be bright if R_(a) and R_(c) are out of phase, they will undergo destructive interference. * Refraction at an interface never changes the phase of the wave. * For reflection at the interface between two media 1 and 2, if n_(1)ltn_(2) the reflected wave will change phase by pi . if n_(1)gtn_(2) the reflected wave will not undergo a phase change. for reference n_(air)=1.00 * if the waves are in phase after refection at all interfaces, then the effects of path length in the film are Constructive interference occur when (n= refractive index) 2t=mlamda//n" "m=0,1,2,3... .. Destructive interference occurs when 2t=(m+1//2)lamda//n" "m=0,1,2,3... Q. The average human eye sees colors with wavelengths between 430 nm to 680 nm. For what visible wavelength will a 350 nm thick n=1.35 soap film produce maximum destructive interference?

Distinguish between : (a) afferent neurons and efferent neurons (b) impulse conduction in an myelinated nerve fibre and unmyelinated nerve fibre (c ) aqueous humour and vitreous humor (d) blind spot and yellow spot (f) cranial nerves and spinal nerves .

The lens governing the behavior of the rays namely rectilinear propagation laws of reflection and refraction can be summarised in one fundamental law known as Fermat's principle. According to this principle a ray of light travels from one point to another such that the time taken is at a stationary value (maximum or minimum). if c is the velocity of light in a vacuum the velocity in a medium of refractive index mu is (c)/(mu) hence time taken to travel a distance l is (mul)/(c) if the light passes through a number of media, the total time taken is ((1)/(c))summul or (1)/(c)intmudl if refractive index varies continuously. Now summul is the total path, so that fermat's principle states that the path of a ray is such that the optical path in at a stationary value. this principle is obviously in agreement with the fact that the ray are straight lines i a homogenous isotropic medium. it is found that it also agrees with the classical laws of reflection and refraction. Q. If refractive index of a slab varies as mu=1+x^(2) where x is measured from one end then optical path length of a slab of thickness 1 m is