Ch\u01b0\u01a1ng 7 – B\u00e0i 43: Hi\u1ec7n t\u01b0\u1ee3ng quang \u0111i\u1ec7n ngo\u00e0i. C\u00e1c \u0111\u1ecbnh lu\u1eadt quang \u0111i\u1ec7n<\/a><\/blockquote><\/iframe>