1969-05-21 — Page 23

育教備華頁三第張六第 日六初月四年歷 WAH KIU YAT PO

郭日僑華

文中學會考試題預習

物理科

(廿九) ·陸永戒

PHYSICS (29).

Solution

6. (a) Total internal reflection

When light passes from one: medium to

more optically dense medium there will always be both reflection and refraction for al1

angles of incident. But this is not always the case when light passes from a more optically. dense medium to a lese optically dense medium. If the angle of incidence increase to a certain angle, the angle of refraction will becomes maximum, 90 degrees. This angle of incedence " is known as the critical angle. In this case, a comparatively weak reflected ray obtained internally in the denser medium and strong refracted ray lies just on the surface discrimination. For angle of fincadence greater than the critical angle, all the light 16. internally reflected. There is no refracti at all. The condition is known as teja tod reflec

(11) For the first and the second cases, there is another Tay of weaker intensity being

reflected and refracted respectively. The

main refracted and reflected rays On and OB are much brighter.

(111) The critical angle is calculated as 1

1/1.5 2/3

41 54

(iv) The angle of refraction made by the way OA·

aini

sin r

sin 2-

3/4 4836)

(d) The tooth to be examined as put within the

focal length of the concave mirror. A magnified, erect and virtual image is formed behind the

90°

(1) When light passes from water to air, and li

the angle of incidence. Le greater than the critical angle, total internal reflection

(ii) Glass is optically denser than air, When

light passes from air to glass there wil} always be both reflection and refraction. No total internal reflection will take par (111) Glass im optically denser than water. When light incedents from glass to water and at an angle of incedience greater than the critical angle, total intemal reflection

7.(a) (1) The reflected rays will pass through

point o again.

(ii) The distance between 0 and the lans L is the

focallength of the lens.

Reasoat Rays incident parallel to the

principal azia will be refracted through the focus.

(b) Refer to any text book of Physics or Biology for the labelled diagram of a human eye.

Accommodation is the ability of the eye to change the focal length of the orystalline lens of the sys so that objects placed at various distances can be focus clearly on the retina of theaya

The losst. distance of uzasañot vision qui tân ɑys is the position of the nearest object that can be seen both clearly and without strain by the unaided sya.

The possession of two eyes glVOR TAG MAYNILVR5= of a binocular vision, that is to give the sense of depth of an object. Esah sya ban a #lightly different view of a given situation. Two of them will judge the distance exaotly.

The light undergoes a successive reflections · from the front surface of the glass and also by multiple internal reflection inside the glass. These parallel beans of ray reflected refruoted are very much weaker than the one formed by the silver surface of the mirror. If the incident ray comes from the reflection of object, you will suffer the disadvantage of a number of extra images formed. This unnecessar images are known as the ghost images. (0) (1)

!

8. (a)

(0) Luminous intensity of the lamp - 180 dif

Intensity of illumination of the desk

- 5 ft-candlas

(Eaight of lamp

Height of lamp - 6 ft

If a plane mirror is placed 1 ft. above the lasp

The new intensity of illumination. E, is

180

180

ft-candle

16

三期星:

日一廿月五年九六九一公年八十五國民痲中

職與校

追到

苦的而

政府嚴加駁斥

光

理

·膠

們做到些打麼?.. | 典政治活動應冷的認識與度們過得

許多勤育學·者及大學們紛紛指出大型教育,

的病徵:

所謂「經師易得,人師殿求。 抽貌的,又怎語業生產領袖,拫當落個 間體製帷的雙社會北,大運選在空翼討論

得實際面有用的側識?卟們應佔地 一個病人坐在牙科醫出的特子上,等待加入些他 已楣大大不同,而大、的湯料料 現在的大徴生可能對,們說:「我們越一亮的版主要的地位,而興,坐在我,好像一能加大學機一刻將有試呢? 方法在敦技學生,又怎他應打當熱的帶止,處在「目標 那察大灣教育的電雄有燃地方明,第一的時代,新的毗會和然潛個城市,但,能和機也殼度實,4後较們必須補宗香港的大學教育,文科試題可以用錢買一事駛斥說:這黑原法,不 第隉聯校與前曾分離;當前的完學,處在第一流款其辭,但法香湖沒有獨立我們大學的颢育目 中文大學是模仿美,培養小英感人。這當然是

·有些人批酒坐大是模仿英柄的,小英

随湳小斑

部安

惱心,使他們在形式的時候能選編出來,而 立思考的朗才干面在搜集許多材料,就剃到標 挝:來目前計æ的,姝顯。. [他們的任務,不在於啟請鵰出對知識的,經和籀 第一傳授知識而非研究學問:有些敎授認爲 學生可不知怎標研究,問。只有坐在椅子上高高一所專研的科目,是每個受敦啞的,所必須战神的一點的改變,自開軍新作適當的安排。 由於現代教育觀念的革新和芬道被评

』 第玩走入了学角尖去·百世部活

現,併

適新;流成瓶

對必一體嚴重,自會通知乎方採取行動。 价玩|城街女二號三樓電話:H二四八八,若事 - 群話 - 縢實稱與小舉動部说出收,審 「不智的人才會買。若任何人有任何證據證明此 宦好那些與會酒試超不同的題目,難圖欺騙金 外就引出學生的不安。唯一可性是一些騙 (┫昨日政府狼图 就外傳中藥會考英 認爲不外意圖引起胰生不安 若有證據請投訴會考部秘?4

(11)

香港私立大學教育應有的全面改革

·英國教育器者查研曼和孔次在他們的教育

吳潘頤

舘品,以爲就难了本份。

擞『你體蜚駹团西外國配?學生雙數分計雜的,然一個學生在四年內只要惨祷

#?

萬年不批

京非迎记

台瞰田

設

問

中

藝

做照編們的號們無操心們的兒女一百四十二個學分,就可以得到位。所沉著有一大半的地位,政府邀中文君,或注册爲離 第二零也良鉍而非憋髅交易:現在六層制裡上泡院,無沾秘决大學學位問題及妥善的離世:一

生述了這些話,心實問閲不樂,因爲他們自己從|整性和柔此和直係, 望我們怎桥遊戲,我們的生活目的选件灣一分爲片斷的學搽面来熊佔席生肼齡團間的 ?沖們监際共同工作?們憑開和他人一起生活以通鼐學識霁称的,是因儒大澳的濮健体察被 第三師生關係脫節,現在的大學教授在敦

告

將香

- 0.52 x 4002

0.5-400

200 GPS

知道

(0.5)

500 o.pls.

教

矯些學學記的臨

有點走入牛角尖去的傾向。 側重於革料發育,而忽略了通才教育。無怪有些· 按整個課程,使學生得到實話,因此有許多大學 |-墨生的彩業文,有過奇僻之處。研冤被爲 擴大受助學校網業及甜加受助名額,使私立大專

·了知識的統一性,很少和其他合作以推學 程應有的功能。 發渺,而不顧到整學校和學生的發展,而忘記時間,馬,鯨構財定贏程標準,以發揮 知識。於是只顧到目己的某種科目或自己學米的一組邀請專家成立大湖程研究委員拿,用-

裕的 激校,亦愛同等规間,同時發給研究費及設置政

The frequenoy of the firet overtone. ia 1500 a.p..

(d) (1) When air has been removed, ringing of the

bell can be heard. Tou oas still see the vibration of the hammer.

This supports that sound travels in a material medium.

MOQUNGIng source 18 placed near to a hollow container, and the frequency of the source is equal to the natural frequency of the container. the container and its content will set into sympathetic vibration. The amplitude of this vibration builds up a sound. This phenomenon is. called resonance.

Example: Radio waves stimulating the electrical

circuit to oscillats.

(b) The experiment using resonance tube to find the

velocity of sound may be found in any Physics text.

Description of the same experiment has been also given in the 21 issue of this column.

air exhausted

(11) A ticking watob is placed near the end of

one tube and the sar on the other Adjustment of the tubes to give a loudest tioking to be heard. Measure the angles. It ie found that the incident and the reflected waves and the normal are in the same plane and the angle of incidence and the angle of reflection are equal, Sound shave the same lave of reflection as light。

{c} (frequency)

f

Tension. Jength

30° is smaller than the critical angle. The incident ray 40 in refracted away from the normal on passing out into air, OA', BO incidents at an angle which is equal to the critical angle of that glass. It will be refracted as OB2 at an angle of refraction of 90 degrees.

CO incidente at an angle greater than the critical angle. Total internal reflection Occurs. OC1 is the reflected ray.

2/ T

(1) (2) 2015 (25 le= la)

(iii) The two travelling waves should be equal

in magnitude, same frequency, and exactly out of phase.

XXXX

D