{"id":835,"date":"2018-02-18T16:33:03","date_gmt":"2018-02-18T08:33:03","guid":{"rendered":"https:\/\/gurumuda.net\/physics\/?p=835"},"modified":"2018-02-18T16:33:03","modified_gmt":"2018-02-18T08:33:03","slug":"optical-instrument-contact-lenses-problems-and-solutions","status":"publish","type":"post","link":"https:\/\/gurumuda.net\/physics\/optical-instrument-contact-lenses-problems-and-solutions.htm","title":{"rendered":"Optical instrument contact lenses \u2013 problems and solutions","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

1. <\/span><\/span>Power of a contact lens<\/a> is <\/span><\/span>-5 <\/span><\/span>D<\/span><\/span>iopt<\/span><\/span>ers<\/span><\/span>. <\/span><\/span><\/p>\n

(a) <\/span><\/span>The contact lens is a converging lens<\/a> or diverging lens<\/a>?<\/p>\n

(b) <\/span><\/span>What is the focal length of the contact lens?<\/p>\n

(c) <\/span><\/span>Nearsighted eye<\/a> or farsighted eye<\/a>? If the nearsighted eye, what then will be the near point?<\/span><\/span><\/p>\n

Known :<\/span><\/span><\/u><\/p>\n

Lens’ power <\/span><\/span>(P) = -5 <\/span><\/span>D<\/span><\/span><\/p>\n

Solution :<\/span><\/span><\/u><\/p>\n

(a) <\/b><\/span><\/span>Converging lens or diverging lens <\/b><\/span><\/span>? <\/b><\/span><\/span><\/p>\n

The minus sign of the lens’ power indicates the contact lens is the diverging lens.<\/span><\/span><\/p>\n

(b) <\/b><\/span><\/span>The focal length? <\/b><\/p>\n

P = 1\/f <\/span><\/span><\/p>\n

-5 = 1\/f<\/span><\/span><\/p>\n

f = 1\/-5 = -0.2 m = -20 cm<\/span><\/span><\/p>\n

The focal length of diverging lens is <\/span><\/span>20 cm.<\/span><\/span><\/p>\n

(c) <\/b><\/span><\/span>Nearsighted eye or farsighted eye ?<\/b><\/span><\/span> <\/b><\/p>\n

-1\/<\/span><\/span>d<\/span><\/span>i <\/span><\/sub>= 1\/f \u2013 1\/<\/span><\/span>d<\/span><\/span>o<\/span><\/sub><\/p>\n

-1\/<\/span><\/span>d<\/span><\/span>i<\/span><\/sub> = -1\/20 \u2013 1\/~ = -1\/20 \u2013 0 <\/span><\/span><\/p>\n

-1\/<\/span><\/span>d<\/span><\/span>i<\/span><\/sub> = -1\/20 <\/span><\/span><\/p>\n

d<\/span><\/span>i<\/span> <\/sub>= 20 cm <\/span><\/span><\/p>\n

The image distance is 20 cm. 20 cm is far point of the<\/span><\/span> farsighted eye. For a normal eye, the far point is infinity.<\/span><\/span><\/p>\n

<\/p>\n

2. <\/span><\/span>Power of a contact lens is <\/span><\/span>1.5 <\/span><\/span>Diopters. <\/span><\/span><\/p>\n

(a) <\/span><\/span>The contact lens is converging lens or diverging lens <\/span><\/span>? <\/span><\/span><\/p>\n

(b) <\/span><\/span>What is the focal length of the contact lens <\/span><\/span>? <\/span><\/span><\/p>\n

(c) <\/span><\/span>Nearsighted eye or farsighted eye ? If farsighted eye, what then will be the far point ?<\/span><\/span><\/p>\n

Known :<\/u><\/span><\/span><\/p>\n

Lens power <\/span><\/span>(P) = 1.5 <\/span><\/span>Diopters<\/span><\/span><\/p>\n

Solution :<\/span><\/span><\/u><\/p>\n

(a) <\/b><\/span><\/span>converging lens or diverging lens<\/b><\/span><\/span><\/p>\n

The plus sign of the lens’ power indicates the contact lens is converging lens.<\/span><\/span><\/p>\n

(b) <\/b><\/span><\/span>The focal length <\/b><\/span><\/span> <\/b><\/p>\n

P = 1\/f <\/span><\/span><\/p>\n

1.5 = 1\/f<\/span><\/span><\/p>\n

f = 1\/ 1.5 = 0.67 m = 67 cm<\/span><\/span><\/p>\n

The focal length of converging lens is <\/span><\/span>67 cm.<\/span><\/span><\/p>\n

(c) <\/b><\/span><\/span>Nearsighted eye or farsighted eye<\/b><\/span><\/span><\/p>\n

-1\/<\/span><\/span>d<\/span><\/span>i<\/span><\/sub> = 1\/f \u2013 1\/<\/span><\/span>d<\/span><\/span>o<\/span><\/sub><\/p>\n

-1\/<\/span><\/span>d<\/span><\/span>i<\/span><\/sub> = 1\/67 \u2013 1\/25 = 25\/1675 – 67\/1675 = -42\/1675 <\/span><\/span><\/p>\n

–<\/span><\/span>d<\/span><\/span>i <\/span><\/sub>= -1675\/42 = -40 cm = -0.40 m<\/span><\/span><\/p>\n

d<\/span><\/span>i <\/span><\/sub>= 40 cm<\/span><\/span><\/p>\n

The image distance<\/a> is 40 cm. 20 cm is near point of the<\/span><\/span> farsighted eye. For a normal eye, the near point is 25 cm.<\/span><\/span><\/p>\n

[wpdm_package id=’868′]<\/p>\n

    \n
  1. Concave mirror problems and solutions<\/a><\/li>\n
  2. Convex mirror problems and solutions<\/a><\/li>\n
  3. Diverging lens problems and solutions<\/a><\/li>\n
  4. Converging lens problems and solutions<\/a><\/li>\n
  5. Optical instrument human eye problems and solutions<\/a><\/li>\n
  6. Optical instrument contact lenses problems and solutions<\/a><\/li>\n
  7. Optical instrument eyeglasses<\/a><\/li>\n
  8. Optical instrument magnifying glass problems and solutions<\/a><\/li>\n
  9. Optical instrument microscope – problems and solutions<\/a><\/li>\n
  10. Optical instrument telescopes problems and solutions<\/a><\/li>\n<\/ol>\n

    <\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

    1. Power of a contact lens is -5 Diopters. (a) The contact lens is a converging lens or diverging lens? (b) What is the focal length of the contact lens? (c) Nearsighted eye or farsighted eye? If the nearsighted eye, what then will be the near point? Known : Lens’ power (P) = -5 D … Read more<\/a><\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_seopress_titles_title":"","_seopress_titles_desc":"","_seopress_robots_index":"","_seopress_robots_follow":"","_seopress_robots_imageindex":"","_seopress_robots_snippet":"","_seopress_robots_primary_cat":"","_seopress_robots_breadcrumbs":"","_seopress_robots_freeze_modified_date":"","_seopress_robots_custom_modified_date":"","_seopress_robots_canonical":"","_seopress_social_fb_title":"","_seopress_social_fb_desc":"","_seopress_social_fb_img":"","_seopress_social_fb_img_attachment_id":0,"_seopress_social_fb_img_width":0,"_seopress_social_fb_img_height":0,"_seopress_social_twitter_title":"","_seopress_social_twitter_desc":"","_seopress_social_twitter_img":"","_seopress_social_twitter_img_attachment_id":0,"_seopress_social_twitter_img_width":0,"_seopress_social_twitter_img_height":0,"_seopress_redirections_value":"","_seopress_redirections_enabled":"","_seopress_redirections_enabled_regex":"","_seopress_redirections_logged_status":"","_seopress_redirections_param":"","_seopress_redirections_type":0,"_seopress_analysis_target_kw":"Optical instrument contact lenses \u2013 problems and solutions","_seopress_news_disabled":"","_seopress_video_disabled":"","_seopress_video":[],"_seopress_pro_schemas_manual":[],"_seopress_pro_rich_snippets_disable_all":"","_seopress_pro_rich_snippets_disable":[],"_seopress_pro_schemas":[],"footnotes":""},"categories":[3],"tags":[],"class_list":["post-835","post","type-post","status-publish","format-standard","hentry","category-solved-problems-in-basic-physics"],"gt_translate_keys":[{"key":"link","format":"url"}],"_links":{"self":[{"href":"https:\/\/gurumuda.net\/physics\/wp-json\/wp\/v2\/posts\/835","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/gurumuda.net\/physics\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gurumuda.net\/physics\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gurumuda.net\/physics\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/gurumuda.net\/physics\/wp-json\/wp\/v2\/comments?post=835"}],"version-history":[{"count":0,"href":"https:\/\/gurumuda.net\/physics\/wp-json\/wp\/v2\/posts\/835\/revisions"}],"wp:attachment":[{"href":"https:\/\/gurumuda.net\/physics\/wp-json\/wp\/v2\/media?parent=835"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gurumuda.net\/physics\/wp-json\/wp\/v2\/categories?post=835"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gurumuda.net\/physics\/wp-json\/wp\/v2\/tags?post=835"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}