Description : A first order reaction A → B occurs in an isothermal porous catalyst pellet of spherical shape. If the concentration of A at the centre of the pellet is much less than at the external surface, the ... A) Diffusion within the pellet (B) Reaction (C) External mass transfer (D) None of the above
Last Answer : (A) Diffusion within the pellet
Description : A mirage occurs because of – (1) Reflection by hot ground (2) Total internal reflection by layers of air (3) Interference of light (4) Diffraction of light
Last Answer : (2) Total internal reflection by layers of air Explanation: A mirage is a naturally occurring optical phenomenon in which light rays are bent to produce a displaced image of distant objects or the ... -changing mirage. Cold air is denser than warm air and has therefore a greater refractive index.
Description : A mirage occurs because of (1) reflection by hot ground (2) total internal reflection by layers of air (3) interference of light (4) diffraction of light
Last Answer : total internal reflection by layers of air
Description : A drop of liquid assumes spherical shape because: (1) Intermolecular forces are strong in liquids (2) A sphere has the least surface area for a given volume (3) A sphere has the largest surface area for a given volume (4) Inter molecular forces are weak in liquids
Last Answer : (2) A sphere has the least surface area for a given volume Explanation: A drop of liquid assumes spherical shape because a sphere has the least surface area for a given volume.
Description : Rain drops acquire spherical shape due to - (1) viscosity (2) surface tension (3) friction (4) elasticity
Last Answer : (2) surface tension Explanation: The Surface tension pulls the surface of the drop equally at all points thus produces the spherical shape having the minimum surface area.
Description : The centre of the reflecting surface of a spherical mirror is called the : (1) Radius (2) Centre of Curvature (3) Pole (4) Focus
Last Answer : (3) Pole Explanation: The center of the reflecting surface of a spherical mirron is called as the pole of the mirror which is mainly known as the center of curvature.
Description : Water drops are spherical because of - (1) viscosity (2) density (3) polarity (4) surface tension
Last Answer : (4) surface tension Explanation: Surface tension is responsible for the shape of liquid droplets. Although easily deformed, droplets of water tend to be pulled into a spherical shape by ... absence of other forces, including gravity, drops of virtually all liquids would be approximately spherical.
Description : Small bubbles are perfectly spherical because of – (1) Gravity (2) Pressure (3) Viscosity (4) Surface tension
Last Answer : (4) Surface tension Explanation: Surface tension is responsible for the shape of liquid droplets. Although easily deformed, droplets of water tend to be pulled into a spherical shape by the cohesive ... shape minimizes the necessary "wall tension" of the surface layer according to Laplace's law.
Description : A spherical ball made of steel when dropped in mercury container will – (1) sink in mercury (2) will be on the surface of mercury (3) will be partly immersed mercury (4) will dissolve in mercury
Last Answer : (2) will be on the surface of mercury Explanation: The density of steel usually ranges between 7.75 and 8.05 g/cm3 and the density of mercury is 13.534 g/cm3. Mercury ... materials usually have different densities, so density is an important concept regarding buoyancy, purity and packaging.
Description : A falling drop of rain water ac-quires the spherical shape due to – (1) Viscosity (2) Surface Tension (3) Atmospheric pressure (4) Gravitational force
Last Answer : (2) Surface Tension Explanation: Raindrops start out as round high in the atmosphere as water collects on dust and smoke particles in clouds. But as raindrops fall, they lose their rounded ... the molecules stick together. The cause is the weak hydrogen bonds that occur between water molecules.
Description : What reflecting surface forms a geometrically perfect image of a point source located at infinity (such as that approximated by a star)? w) Paraboloid x) Ellipsoid y) spherical z) Hyperboloid
Last Answer : ANSWER: W -- PARABOLOID
Last Answer : A sphere has the least surface area for a given volume
Description : Small bubbles are perfectly spherical because of (1) Gravity (2) Pressure (3) Viscosity (4) Surface tension
Last Answer : Surface tension
Description : A spherical ball made of steel when dropped in mercury container will (1) sink in mercury (2) will be on the surface of mercury (3) will be partly immersed mercury (4) will dissolve in mercury
Last Answer : will be on the surface of mercury
Description : A falling drop of rain water acquires the spherical shape due to (1) Viscosity (2) Surface Tension (3) Atmospheric pressure (4) Gravitational force
Last Answer : Surface Tension
Last Answer : The rainbow is full of internal reflection
Description : If a light ray IM is incident on the surface AB as shown, identify the correct emergent ray. light-reflection-and-refraction-chapter-wise-important-questions-class-10-science-8 -Physics
Last Answer : Ray NQ, as it has to be parallel to ray OS.
Description : A light wave is incident over a plane surface with velocity x. After reflection the velocity becomes- (1) x/2 (2) x (3) 2x (4) x/4
Last Answer : (2) x Explanation: When a ray of light incident on a boundary separating two media comes back into the same media, this phenomenon, is called reflection of light. After reflection velocity, wavelength and frequency of light remains same but intensity decreases.
Description : Light waves projected on oil surface show seven colours due to the phenomenon of (1) polarisation (2) refraction (3) reflection (4) interference
Last Answer : (4) interference Explanation: In physics, interference is a phenomenon in which two waves superpose to form a resultant wave of greater, lower, or the same amplitude.
Description : A thin oil film on a water surface appears coloured because of – (1) reflection (2) interference (3) diffraction (4) polarization
Last Answer : (2) interference Explanation: A thin oil film on a water surface appears coloured because of thin-film interference which involves the interference of light waves reflecting off the top surface of a film with the waves reflecting from the bottom surface.
Description : According to standard convention, the angles of incidence and reflection for a plane surface are measured from: w) the reflecting surface x) lines at 45 degrees to the reflecting surface y) a line at 90 degrees to the reflecting surface z) there is no standard
Last Answer : ANSWER: Y -- A LINE AT 90 DEGREES TO THE REFLECTING SURFACE
Description : When light is reflected from a surface, the angle of incidence is: w) 30 degrees x) equal to the angle of reflection y) 90 degrees z) 180 degrees
Last Answer : ANSWER: X -- EQUAL TO THE ANGLE OF REFLECTION
Description : A light wave is incident over a plane surface with velocity x. After reflection the velocity becomes :
Last Answer : x
Description : A thin oil film on a water surface appears coloured because of (1) reflection (2) interference (3) diffraction (4) polarization
Last Answer : interference
Description : What kind of reflection does a convex lens produce ?
Last Answer : Convex or convergent lenses form real and inverted reflections.
Description : ECE Board Exam March 1996 ___________ occurs when the microwave beam is at point of grazing over an obstacle. A. Diffraction B. Refraction C. Absorption D. Reflection
Last Answer : A. Diffraction
Description : When a beam of light travels through media of two different densities, if theangle of incidence isgreater than the critical angle, _______ occurs. A) reflection B) refraction C) incidence D) criticism
Last Answer : reflection
Description : Standing waves occurs due to a) Impedance match b) Impedance mismatch c) Reflection d) Transmission
Last Answer : b) Impedance mismatch
Description : What name is given to the angle where total internal reflection occurs?
Last Answer : Critical angle of incidence.
Description : The radius of a spherical balloon increases from 7cm to 14cm as air is being pumped into it. Find the ratio of surface areas of the balloon in the two cases. -Maths 9th
Last Answer : Let r1 and r2 be the radii of spherical balloon and spherical balloon when air is pumped into it respectively. So r1 = 7cm r2 = 14 cm Now, Required ratio = (initial surface area)/(Surface area after pumping air into ... = (7/14)2 = (1/2)2 = ¼ Therefore, the ratio between the surface areas is 1:4.
Description : A spherical ball is divided into two equal halves. If the curved surface area of each half is 56.57 cm?, find the volume of the spherical ball.11531/cylinder-radius-halved-and-height-doubled-then-find-volume-with-respect-original-volume -Maths 9th
Last Answer : since curved surface of half of the spherical ball = 56.57 cm2 ∴ 2πr2 = 56.57 ⇒ r2 = 56.57 / 2 × 3.14 = 9 ⇒ r = 3 cm Now, volume of spherical ball = 4 / 3 πr3 = 4 / 3 × 3.14 × 3 × 3 × 3 = 113.04 cm3
Description : A spherical metal of radius 10 cm is melted and made into 1000 smaller spheres of equal sizes. In this process the surface area of the -Maths 9th
Last Answer : Option (C) is correct. Solution: Let the radius of the small spheres be r' cm. Volume of metal remains the same in both cases. So, vol of the spherical metal of radius 10 cm = total ... Total Surface area of 1000 smaller spheres: 1000*4π12 = 4000π Hence, the surface area increased by 10 times.
Description : What is the midpoint of the reflector surface of a spherical mirror called ?
Last Answer : The center point of the reflecting surface of a spherical mirror is called pole.
Description : The volume of a spherical balloon is increasing at a rate of ` 25 cm^(3)//sec`. Find the rate of increase of its curved surface when the radius of bal
Last Answer : The volume of a spherical balloon is increasing at a rate of ` 25 cm^(3)//sec`. Find the ... its curved surface when the radius of balloon is 5 cm.
Description : A spherical convex surface separates object and image space of refractive index `1.0 and 4/3.` If radius of curvature of the surface is `10cm,` find i
Last Answer : A spherical convex surface separates object and image space of refractive index `1.0 and 4/3.` If ... of the surface is `10cm,` find its power.
Description : For a non-spherical particle, the sphericity (A) Is defined as the ratio of surface area of a sphere having the same volume as the particle to the actual surface area of the particle (B) Has ... of volume of a sphere having the same surface area as the particle to the actual volume of the particle
Last Answer : (A) Is defined as the ratio of surface area of a sphere having the same volume as the particle to the actual surface area of the particle
Description : If dp is the equivalent diameter of a non-spherical particle, Vp its volume and sp its surface area, then its sphericity is φs is defined by (A) φs = 6 Vp /dpsp (B) φs = Vp /dpsp (C) φs = 6 dpSp /Vp (D) φs = dpSp /Vp
Last Answer : (A) φs = 6 Vp /dpsp
Description : Sphericity is the ratio of the surface area of a spherical particle having the same volume as the particle to the surface area of the particle. Which of the following has the maximum value of sphericity? (A) Sphere (B) Cube (C) Cylinder (L/D = 1) (D) Raschig rings
Last Answer : (A) Sphere
Description : The specific surface of spherical particles is given by (where D and ρ are diameter and density of particle). (A) 6/D.ρ (B) 2/D.ρ (C) 4/D.ρ (D) 12/D.ρ
Last Answer : (A) 6/D.ρ
Description : Sphericity for a non-spherical particle is given by (where, V and S are volume and surface area respectively of one particle. and, D = equivalent diameter of particle). (A) 6.V/D.S (B) V/6D.S (C) D.S/V (D) V/D.S
Last Answer : (B) V/6D.S (C) D.S/V (D) V/D.S
Description : The specific surface of spherical particles is proportional to (where, Dp = diameter of particle). (A) D2 p (B) Dp (C) 1/Dp (D) 1/D2p
Last Answer : (C) 1/Dp
Description : The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface) (A) K/h0 (B) 2K/h0 (C) h0 /K (D) h0 /2K
Last Answer : (B) 2K/h0
Description : Gauss law can be evaluated in which coordinate system? a) Cartesian b) Cylinder c) Spherical d) Depends on the Gaussian surface
Last Answer : d) Depends on the Gaussian surface
Description : The divergence theorem for a surface consisting of a sphere is computed in which coordinate system? a) Cartesian b) Cylindrical c) Spherical d) Depends on the function
Last Answer : d) Depends on the function
Description : The fluid property which matters for falling rain drops to acquire spherical shape is its (A) Pressure (B) Height of descend (C) Viscosity (D) Surface tension
Last Answer : (D) Surface tension
Description : A spherical porous catalyst particle of radius R is subjected to reactant A which reacts to form B by a zero order surface reaction A → B. Film mass transfer resistance is negligible and pore diffusion of A ... (D) Effectiveness factor for a zero order reaction cannot be 7/8 as it must always be 1
Last Answer : (A) Inner catalyst core of radius R/8 does not participate in reaction (
Description : Surface tension of a liquid (A) Is due to intermolecular forces of cohesion (B) Decreases with rise in temperature (C) Is responsible for the spherical shape of an isolated liquid drop (D) All (A), (B) & (C)
Last Answer : (D) All (A), (B) & (C)
Description : Spherical shape of mercury droplets is due to its (A) High viscosity (B) Low surface tension (C) High density (D) High surface tension
Last Answer : Option D