Science Grade 8 Questions

21. How does light normally travel? A. in a straight line B. in concentric circles C. always toward a dark area D. in a curved line 22. The line perpendicular to the reflective surface is the __________.

26. A 10-cm object has a 20-cm image. What is the magnification? A. 10 C. 20

B. 2 D. 0.5

27. What is f if you have an object 2.0 m from the concave mirror, and the image is 4.0 m from the mirror?

A. line of reflection B. line of incidence C. normal D. line of refraction

A. 2 m C. 4 m

23. You are standing in front of a bathroom mirror. Where is your image located? A. behind you B. in front of the mirror C. behind the mirror D. between you and the mirror 24. Which type of mirror produces an image that is always erect, always the same height as the object, and always virtual? A. diffuse C. plane

D. converge and sight lines converge and form a real image

B. concave D. convex

25. When an object is placed between the focal point and a concave mirror, the rays __________. A. diverge and sight lines diverge and form a real image B. converge and sight lines diverge and form a virtual image C. diverge and sight lines converge and form a virtual image

B. 1.3 m D. 0.67 m

28. A photo is held 25 cm from a convex lens with a focal length of 30 cm. What is the image position of the photo? A. – 150 cm C. 5 cm

B. 150 cm D. – 50 cm

29. An object is placed in front of a convex lens with a 7.00-cm focal length, If the object distance is 15.0 cm, what is the image distance? A. 2.75 cm C. 8.00 cm

B. 4.77 cm D. 13.1cm

30. Which describes the image produced by a concave lens? A. reduced and real B. enlarged and real C. reduced and virtual D. enlarged and virtual

An object is placed in front of a concave lens with a 6 cm focal length, If the object distance is 12 cm and the height is 4 cm. 31. What is the distance of the image? A. 10 cm C. 12 cm

B. 11 cm D 14 cm

32. What is the magnification? A. 1 x C. 3 x

B. 2 x D. 4 x

33. Look at the following picture!

35. An object is placed in front of a concave lens with a 20 cm focal length, If the object distance is 30, what is the image’s distance? A. 60 cm in front of the lens B. 60 cm behind the lens C. 12 cm in front of the lens D. 12 cm behind the lens 36. In what part of the eye is light primarily focused?

The refraction angle is showed by… A. p C. r

B. q D. s

34. The following is the correct special rays in convex lens, except…

A. lens C. cornea

B. optic nerve D. retina

37. What is happening in the condition called hyperopia? A. The image is focused past the retina. B. The image is focused in front of the retina C. The lens is not able to focus the images. D. The cornea has lost its ability to focus images. 38. What is a function of the prisms in binoculars? A. separate wavelengths of light B. invert the image C. increase the focal length D. reduce aberration

39. Why would a camera use an achromatic lens?

A. neutral C. positive

A. to focus on far away objects B. to reduce spherical aberration C. to reduce chromatic defect D. to filter out light with too much intensity

45. The atomic mass of an element is __________ of that element.

40. In a microscope, what is the object for the eyepiece? A. the subject being studied B. the light source C. the image from a prism D. the image from the objective lens 41. The smallest part of an element that can not be chemically reacted is called… A. atom C. molecule

B. element D. electron

42. An atom containing six positive charges and six negative charges has __________ charge. A. a strong negative B. a positive C. a negative D. no net 43. The __________ of an element is the number of __________ of an atom of that element. A. atomic mass, electrons in the nucleus B. atomic number, protons in the nucleus C. mass number, protons plus neutrons in the outermost energy level D. mass number, neutrons in the nucleus 44. If a neutral atom releases its electron, the atom will become…

B. negative D. zero

A. the number of electrons in each atom B. the number of protons plus the number of neutrons of an atom C. the average mass of an atom D. the number of protons in each atom 46. __________ are atoms of the same element that have different numbers of neutrons. A. Isotopes C. Compounds

B. Beta particles D. Alpha particles

47. Which of the following is the correct chemical symbol for carbon? A. Ca C. C

B. Co D. Cu

48. Atoms consist of a positively charged center called a(n) __________. A. electrons C. neutrons

B. nucleus D. protons

49. The atomic number of manganese is 25; its mass number is 55. How many neutrons does an atom of manganese have in its nucleus? A. 80 B. 25 C. 30 D. 55 50. Fluor atom which receives 1 electron will become… A. F+ C. F-

B. F2+ D. F2-