1987-10-01 — Page 24

頁四第張六第

物理(一)

報日僑華

WAH KIU YAT PO

curvature àré

reflected back along their own paths.

(v)

image

u <f

P

object F

(b) Convex mirror

P

日九 初月八年卯丁曆夏

1988中學會考 試題預習專欄

明遉出版社

MILL & DALE PRESS

Revision Exercises

for

Cert. Exam. (1988)

PHYSICS (1) -

This course provides the candidates of IKCEE 1988

a general revision in Physics. Brief notea

and revision exercise

SECTION A OPTICS

Chapter One Reflection

1.1 Reflection at plane

surfaces,

Law of Reflection

1. The incident ray, the reflected ray and the normal at the point of

incidence are on the same plane.

2. The angle of

incidence is equal to the angle of reflection. (i.e.

Zi- ¿r)

reflected raya reċaived by the abserver. The reflected rays appear to diverge from 1,

which is the image of

the object. The image is virtual.

Note: A real image is

one through

which the actual

light rays pass

(ie, it can be

put on a

screen.) An virtual image is one from

which light

rays appear to diverge (i.e.

it connot be

put on a screen).

Properties of image formed by plane mirror,

(i) virtual (ii) eract

(111) laterally

inverted

some size na the object

as far behind

the mirror, as

the object is in traht.

1.2 Reflection at curved

mirrors.

Spherical curved mirrors

Spherical concave mirror

2. Raya parallel to the principal axis are reflected so

ав to

pass through the focus for concave mirror and appear to diverge from the focus for convex mirror.

3. Rays through the

concave

focus of a mirror, or rays towards the focus of a convex mirror, are reflected parallel to the principal axis.

Example:

Find graphically, the nature of the image forced by an object

5 cm tall, placed 40 cm in front of a concave mirror of focal length 15 cu.

ADE:

The image is real,

inverted and diminished. It's a size is 3 cm. (a) Concave mirror

The nature of an image formed by a

concave mirror vary with difference in position

of the object.' In the following ray diagrams, C. F and P are the

centre of curvature, focus and the pole of the concave mirror respectively.

Let u-object distance

v-image distance

and f-focal length

Ray diagrams

(4) u>21

object

for each section are for revision purpose. Solutions for exercises after each section will

(iv)

be given in the

(*)

following weeks.

incident ray

Plane Mirror

reflected ray

When an object is placed in front of a plane mirror, all the reflected ray, when produced backwards, vill meet a point. behind the mirror. This point is called the image of the

objeat. As shown in

sthe-ray, diagram i

*below* me

the

Spherical convex mirrer

A spherical mirror is one whose reflecting surface is part of the surface of a sphere. The centre of curvature is the centre of the sphere. The radius of the sphere is the radius of curvature of the mirror. The principal focus of a spherical. mirror is the point on the principal axis to which wi1 rays parallel and close to the principal azía converge.

or from which they appear to diverge) after reflection from the mirror. If the focal length of a spherical

mirror (concave or

convex) is fand the rading of curvation is Rthen

Ray diagrams are dravo

according to the rules

liated below:

12 Rays passing through

the centre-of

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inaga

P

(ii)

(111):27

object

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中心2110章:旺角彌敦道六五五號胡社生行1412重型

inage

F

C

حرجية

magnified.

magnified i

virtual, erect, diminished and behind the mirror.

f_v=f

I real

u > 27

u=2]

[ £<v <2f

|_ real

inverted diminished

real

t<u < 21

> 21

real

inverted

inverted

same aize

erect

The properties of the images formed by concave and convex mirrors:

one point

B) A

化學(一)

曜您出版业

MILLI DALE PRESS

Revision. Exercises

for

Cert. Exam (1988)".

CHEMISTRY. (1)

question 1

Part of the Periodic Table is shown below withi some of the first twenty elements being represented by letters. which are not the chemical symbols of the elements.

ajd

(a) Give the letter of

the element

(1) which consists of

monatomic molecules;

(ii) which is

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strongest reducing

agent among the

elements shown;

(iii)which is the best

electro bcrépter

among the elements shown; (iv) which consists of a

€ €

giant covalent lattice of atoma?

Give the name of

the family to which the elements a, b and c belong; (i) the family to which

(c)

the elements x

and y belongi

Arrange the elements a, b and c, in the order of decrossing metallic character.

(d) Why do the elementa

b and c, being placed in the same vertical column,

show similar chomi cal properties?

(e) The element y can

combine separately with the elements b

and e to give the compounds P and respectively.

(1) Using the outermost

shell only, draw

diagrama to show

the electronic

structures of P and

4.

(ii) Explain why P is a

solid but is s liquid at room temperature and pressure,

(iii)Explain briefly why

in liquid state P can conduct electricity while

Q cannot do so.

(f) Using the letters.

only, give the

formula of the

compound formed by

the elements.

(4) and f;

g and b.

What is the

axidation number of

the slopent yuin the following compounds of y, where 0 and Ne are the chemica symbols of hydrogen, oxygen and solum respectively, (1) 0

(2) Na205?

(ii) Whet is the change

in the oxidation number of yin converting H.0 to

(111)TS BO

oxidized

reduced in the procese in (11)? Why?

Question "2-

In the experiment as shown below, the colour- less gas A, formed by de action of concentrated sulphuric acid, on sódium chloride crystals, was passed over a hot iron coil. After some while a solid B was obtained

and a colourless gas Cas

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collected, which could

form an explosive

mixture with air.

iron coil_______salið k

conc. SO

heat

Éas A ↑

Water

watpos

chloride

crystals

Identify and name

(a)

the substances A, H and C respectively.

(b)

Give an equation

for

(i)

the formation of gas Ai

(ii) the reaction between

(c)

gas A and the iron coil.

Give a reason why solid B was

collected at the place as shown, but not near or on the iron coil.

Question 3

(a) A colourless liquid X boils at 46oC and one atmospheric pressure, and burne readily in air. On analysis it is found to consist of 15.8% of carbon and 84.2% of sulphur by mass. (A: C-12, S-32)

(1)

Calculate the empirical formule of X. (ii) It is found the

0.38 g of X, when vaporized, occupies

a volume of 448 cm2 at s.t.p.. What is its molecular formula?

3

(iii)Give an equation of

the complete combustion of X in

air.

(iv) Whea 2.11 g of

liquid X is completely burut in 1000 cm3 of oxygen, what would be the change in the volume?(All volumes of gases are measured at the: same pressure and; temperature,

(b).

lution X Is māde by dissolving dry hydrogen chloride. gas in water while

solution X is made by dissolving dry- hydrogen chloride in dry methylbenzene. (i) State the type of

bond present In hydrogen chloride. (ii) Draw a diagram to

show the electronic. structure of enda hydrogen chloride. (iii)Solution X turns the pH paper red

while solution Y. does not. Explain.

why this is 10..

(d) What would you

observe when a piece of pH. paper is moistened with the water in the trough at the end of the experiment? Explain briefly your answer.

(e) A pale-green

solution D was obtained on

dissolving some of the solid B in water.

(i) What chemical species

was responsible for the colour of the solution D?

(ii) What would you

(1)

(g)

(i)

observe on passing an excess of chlorine gas into the solution D? Explain briefly your observation, giving an ionic equation of the change(s) observed,

if 1.27 g of solid B was obtained at the

end of the

experiment, what would be the

theoretical volume

of gas C collected, measured at a.t.p., in the goa jar?

What would be collected over

water in the gas jar if the iron coil was substituted, in turn, by

zinc powder; (11) copper coil?

If there is n reaction give an equation of the reaction.

If there is NO reaction, explain briefly.

(iv) What would you

observe on passing dry ammonia gas separately into the nolutions X and Y? Explain briefly your observation, (v) Solution X and Y

are placed in turn in the beaker as show below.

battery

bulb

beaker

-solution.

The bulb gives light only when anlution X is put in the beaker. Explain briefly."--

(2) What would be formed

at the cathode und anode respectively on passing a current through ana concentrated solution of X in the above set-up?" Give ionic equations

of the reactions at

the electrodes,

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