Hai tấm kim loại A, B hình tròn được đặt gần nhau, đối diện và cách điện nhau. A được nối với cực âm và B được nối với cực dương của một nguồn điện một chiều. Để làm bứt các e từ mặt trong của tấm A, người ta chiếu chùm bức xạ đơn sắc công suất 4,9mW mà mỗi photon có năng lượng 9,8.10^-19 J vào mặt trong của tấm A này. Biết rằng cứ 100 photon chiếu vào A thì có 1 e quang điện bị bứt ra. Một số e này chuyển động đến B để tạo ra dòng điện qua nguồn có cường độ 1,6A. Phần trăm e quang điện bức ra khỏi A không đến được B là :          

Hai tấm kim loại A, B hình tròn được đặt gần nhau, đối diện và cách điện nhau. A được nối với cực âm và B được nối với cực dương của một nguồn điện một chiều. Để làm bứt các e từ mặt trong của tấm A, người ta chiếu chùm bức xạ đơn sắc công suất 4,9mW mà mỗi photon có năng lượng 9,8.10^-19 J vào mặt trong của tấm A này. Biết rằng cứ 100 photon chiếu vào A thì có 1 e quang điện bị bứt ra. Một số e này chuyển động đến B để tạo ra dòng điện qua nguồn có cường độ 1,6A. Phần trăm e quang điện bức ra khỏi A không đến được B là :          

Ánh sáng có tần số lớn nhất trong số các ánh sáng đơn sắc: Đỏ, lam, chàm, tím là ánh sáng             

Hiện tượng quang điện ngoài là hiện tượng êlectron bị bứt ra khỏi tấm kim loại khi:         

Catôt của một tế bào quang điện có công thoát electron A = 1,188 eV. Chiếu một chùm ánh sáng có bước sóng vào catôt này thì hiện tượng quang điện xảy ra. Để triệt tiêu hoàn toàn dòng quang điện thì hiệu điện thế hãm có độ lớn 1,15 V. Nếu cho UAK = 4 V thì động năng lớn nhất của electron khi tới anôt bằng bao nhiêu?          

Người ta dùng một Laze hoạt động dưới chế độ liên tục để khoan một tấm thép. Công suất của chùm laze là P = 10 W, đường kính của chùm sáng là 1 mm. Bề dày tấm thép là e = 2 mm và nhiệt độ ban đầu là 300C. Biết khối lượng riêng của thép D = 7800 kg/m3 ; Nhiệt dung riêng của thép c = 448 J/kg.độ ; nhiệt nóng chảy của thép L = 270 kJ/kg và điểm nóng chảy của thép tc = 15350C. Thời gian khoan thép là  

Chọn ý sai. Bức xạ điện từ có tần số càng lớn sẽ:

Trong thí nghiệm về hiệu ứng quang, người ta có thể làm triệt tiêu dòng quang điện bằng cách dùng một hiệu điện hãm có giá trị bằng 3,2V. Người ta tách ra một chùm hẹp các quang electrôn và hướng nó đi vào một từ trường đều có cảm ứng từtheo phương vuông góc với các đường sức từ. Bán kính quỹ đạo lớn nhất của các electrôn là ?           

Chiếu một chùm bức xạ có bước sóng vào bề mặt một tấm nhôm có giới hạn quang điện . Hiện tượng quang điện không xảy ra nếu bằng.         

Question 34: 

A tiny village school is soon to celebrate its 110 birthday - against all expectations. Five years ago it seemed certain to close but parents and other villagers fought the local education authority and raised funds to keep it (31)_______. It is now ending its first term as a school (32)_____by the village community and the villagers are just proud of their achievement. They were furious when education chiefs tried to make them send the village children to other schools further away because the number of pupils at the village school was too (33)_____. The villagers started a huge campaign to (34) _____money. They collected enough to hire a teacher and begin to help with school cleaning, lunch supervision and lessons. Now the school is doing well and it seems (35)____ it will continue to run in the future. 

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 36 to 40:

Sugar tastes sweet because of thousands of receptors on the tongue which connect the substance with the brain. The taste of sweetness is universally accepted as the most pleasurable known, although it is a fructose. Abundant is the most common occurring sugar, (36)______ of which include fruit and honey. Sucrose, which supplies glucose to the body, is (37)______ from the sugar cane plant, and white sugar (pure sucrose) is used by food technologists to (38)______ sweetness in other substances. Approximately a dozen artificial sweeteners have been discovered; one of the earliest was Sorbitol from France. Manufacturers add large amounts of sugar to foodstuffs but never more than the (39)______ required to produce the optimum pleasurable taste. Surprisingly, this amount is similar for different people and in different cultures. No one has (40)______ discovered a way to predict whether a substance will taste sweet, and it was by chance alone that all the man-made chemical sweeteners were found to be sweet.

Question 40:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 36 to 40:

Sugar tastes sweet because of thousands of receptors on the tongue which connect the substance with the brain. The taste of sweetness is universally accepted as the most pleasurable known, although it is a fructose. Abundant is the most common occurring sugar, (36)______ of which include fruit and honey. Sucrose, which supplies glucose to the body, is (37)______ from the sugar cane plant, and white sugar (pure sucrose) is used by food technologists to (38)______ sweetness in other substances. Approximately a dozen artificial sweeteners have been discovered; one of the earliest was Sorbitol from France. Manufacturers add large amounts of sugar to foodstuffs but never more than the (39)______ required to produce the optimum pleasurable taste. Surprisingly, this amount is similar for different people and in different cultures. No one has (40)______ discovered a way to predict whether a substance will taste sweet, and it was by chance alone that all the man-made chemical sweeteners were found to be sweet.

Question 39:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 36 to 40:

Sugar tastes sweet because of thousands of receptors on the tongue which connect the substance with the brain. The taste of sweetness is universally accepted as the most pleasurable known, although it is a fructose. Abundant is the most common occurring sugar, (36)______ of which include fruit and honey. Sucrose, which supplies glucose to the body, is (37)______ from the sugar cane plant, and white sugar (pure sucrose) is used by food technologists to (38)______ sweetness in other substances. Approximately a dozen artificial sweeteners have been discovered; one of the earliest was Sorbitol from France. Manufacturers add large amounts of sugar to foodstuffs but never more than the (39)______ required to produce the optimum pleasurable taste. Surprisingly, this amount is similar for different people and in different cultures. No one has (40)______ discovered a way to predict whether a substance will taste sweet, and it was by chance alone that all the man-made chemical sweeteners were found to be sweet.

Question 38:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 36 to 40:

Sugar tastes sweet because of thousands of receptors on the tongue which connect the substance with the brain. The taste of sweetness is universally accepted as the most pleasurable known, although it is a fructose. Abundant is the most common occurring sugar, (36)______ of which include fruit and honey. Sucrose, which supplies glucose to the body, is (37)______ from the sugar cane plant, and white sugar (pure sucrose) is used by food technologists to (38)______ sweetness in other substances. Approximately a dozen artificial sweeteners have been discovered; one of the earliest was Sorbitol from France. Manufacturers add large amounts of sugar to foodstuffs but never more than the (39)______ required to produce the optimum pleasurable taste. Surprisingly, this amount is similar for different people and in different cultures. No one has (40)______ discovered a way to predict whether a substance will taste sweet, and it was by chance alone that all the man-made chemical sweeteners were found to be sweet.

Question 37:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 36 to 40:

Sugar tastes sweet because of thousands of receptors on the tongue which connect the substance with the brain. The taste of sweetness is universally accepted as the most pleasurable known, although it is a fructose. Abundant is the most common occurring sugar, (36)______ of which include fruit and honey. Sucrose, which supplies glucose to the body, is (37)______ from the sugar cane plant, and white sugar (pure sucrose) is used by food technologists to (38)______ sweetness in other substances. Approximately a dozen artificial sweeteners have been discovered; one of the earliest was Sorbitol from France. Manufacturers add large amounts of sugar to foodstuffs but never more than the (39)______ required to produce the optimum pleasurable taste. Surprisingly, this amount is similar for different people and in different cultures. No one has (40)______ discovered a way to predict whether a substance will taste sweet, and it was by chance alone that all the man-made chemical sweeteners were found to be sweet.

Question 36:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 17 to 21:

During the last 400 years, most scientists have (17) ________on mathematics in their development of their inventions or discoveries. However, one great British scientist, Michael Faraday, did not make (18)__________of mathematics. Faraday, the son of a poor blacksmith, was born in London in 1791 and had no (19) ______beyond reading and writing. In 1812 Faraday was hired as a bottle washer by the great chemist Humphry Davy. Later, Faraday became a greater scientist than Davy, making the last years of Davy's life embittered (20) __________ jealousy. Faraday made the first (21)__________motor in 1821, a device that used electricity to produce movement. 

Question 20:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 17 to 21:

During the last 400 years, most scientists have (17) ________on mathematics in their development of their inventions or discoveries. However, one great British scientist, Michael Faraday, did not make (18)__________of mathematics. Faraday, the son of a poor blacksmith, was born in London in 1791 and had no (19) ______beyond reading and writing. In 1812 Faraday was hired as a bottle washer by the great chemist Humphry Davy. Later, Faraday became a greater scientist than Davy, making the last years of Davy's life embittered (20) __________ jealousy. Faraday made the first (21)__________motor in 1821, a device that used electricity to produce movement. 

Question 21:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 17 to 21:

During the last 400 years, most scientists have (17) ________on mathematics in their development of their inventions or discoveries. However, one great British scientist, Michael Faraday, did not make (18)__________of mathematics. Faraday, the son of a poor blacksmith, was born in London in 1791 and had no (19) ______beyond reading and writing. In 1812 Faraday was hired as a bottle washer by the great chemist Humphry Davy. Later, Faraday became a greater scientist than Davy, making the last years of Davy's life embittered (20) __________ jealousy. Faraday made the first (21)__________motor in 1821, a device that used electricity to produce movement. 

Question 17:

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 17 to 21:

During the last 400 years, most scientists have (17) ________on mathematics in their development of their inventions or discoveries. However, one great British scientist, Michael Faraday, did not make (18)__________of mathematics. Faraday, the son of a poor blacksmith, was born in London in 1791 and had no (19) ______beyond reading and writing. In 1812 Faraday was hired as a bottle washer by the great chemist Humphry Davy. Later, Faraday became a greater scientist than Davy, making the last years of Davy's life embittered (20) __________ jealousy. Faraday made the first (21)__________motor in 1821, a device that used electricity to produce movement. 

Question 18: